Xubuntu: Broken "Software & Updates" after mistakenly using Debian.org sources

Mixing sources between disruptions will not work. The dependencies will also be needed and files may modify configuration files and make them useless to other programs.

I suggest you reinstall. You will get back to square one and the OS will work as expected. Ubuntu is based on Debian but it isn't Debian and the packages don't mix at all.

You can restore your user data from your backups.

Reinstalling from scratch would of course be the best solution, but maybe it is not required.

The package management troubleshooting procedure seems to have already cleaned up some of your problems.

What output do you now get for

sudo apt-get update
sudo apt-get dist-upgrade

Did you want to build the locales package locally because of the
"perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:"
warning messages?

What is the output of the command
apt-cache policy locales libc-bin perl

andrew: Yep, I realize that now. I will not forget it, that's for sure. Thanks for the reply.

I still would like to try to get it cleaned up, if at all possible. I have spent quite a bit of time
customizing Xubuntu and despite all my research I don't have a good simple clean system
backup. Backing up my documents is not a problem.

Manfred: The only thing I can see is that "locales" is still missing. I had tried, before I posted
here, to install it without success. That's when "Software Updater" and/or "Software & Updates"
broke.
-------------------------------------------------------------------------
mon-username@mon-ordi:~$ sudo apt-get update
[sudo] password for mon-username:
Ign http://extras.ubuntu.com trusty InRelease
Hit http://extras.ubuntu.com trusty Release.gpg
Hit http://extras.ubuntu.com trusty Release
Hit http://extras.ubuntu.com trusty/main Sources
Hit http://extras.ubuntu.com trusty/main amd64 Packages
Hit http://extras.ubuntu.com trusty/main i386 Packages
Ign http://archive.ubuntu.mirror.rafal.ca trusty InRelease
Ign http://extras.ubuntu.com trusty/main Translation-en
Ign http://archive.ubuntu.mirror.rafal.ca trusty-updates InRelease
Ign http://archive.ubuntu.mirror.rafal.ca trusty-security InRelease
Hit http://archive.ubuntu.mirror.rafal.ca trusty Release.gpg
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates Release.gpg
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security Release.gpg
Hit http://archive.ubuntu.mirror.rafal.ca trusty Release
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates Release
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security Release
Hit http://archive.ubuntu.mirror.rafal.ca trusty/main amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/restricted amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/universe amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/multiverse amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/main i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/restricted i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/universe i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/multiverse i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/main Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty/multiverse Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty/restricted Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty/universe Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/main amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/restricted amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/universe amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/multiverse amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/main i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/restricted i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/universe i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/multiverse i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/main Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/multiverse Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/restricted Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/universe Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/main amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/restricted amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/universe amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/multiverse amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/main i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/restricted i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/universe i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/multiverse i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/main Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/multiverse Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/restricted Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/universe Translation-en
Ign http://archive.canonical.com trusty InRelease
Hit http://archive.canonical.com trusty Release.gpg
Hit http://archive.canonical.com trusty Release
Hit http://archive.canonical.com trusty/partner Sources
Hit http://archive.canonical.com trusty/partner amd64 Packages
Hit http://archive.canonical.com trusty/partner i386 Packages
Hit http://archive.canonical.com trusty/partner Translation-en
Reading package lists... Done
mon-username@mon-ordi:~$ sudo apt-get dist-upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages were automatically installed and are no longer required:
  linux-headers-3.16.0-30 linux-headers-3.16.0-30-generic
  linux-image-3.16.0-30-generic linux-image-extra-3.16.0-30-generic
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
mon-username@mon-ordi:~$ apt-cache policy locales libc-bin perl
locales:
  Installed: (none)
  Candidate: 2.13+git20120306-12.1
  Version table:
     2.13+git20120306-12.1 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     2.13+git20120306-12 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
libc-bin:
  Installed: 2.19-0ubuntu6.6
  Candidate: 2.19-0ubuntu6.6
  Version table:
 *** 2.19-0ubuntu6.6 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/main amd64 Packages
        100 /var/lib/dpkg/status
     2.19-0ubuntu6 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
perl:
  Installed: 5.18.2-2ubuntu1
  Candidate: 5.18.2-2ubuntu1
  Version table:
 *** 5.18.2-2ubuntu1 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status
mon-username@mon-ordi:~$
-------------------------------------------------------------------------
Thanks for the help.

What is the output of

sudo dpkg --audit
sudo apt-get install locales

Another thing now is I have a "Software Updater" window asking me to restart. There's a
Settings button also which I tried and the state of "Software & Updates" is the same as what I described in my OP.

Maybe restarting will repair it. I'm leaving it as is without restarting for now.
...
And now, while I'm writing this, the restart window (Software Updater) has changed to
"Not all updates can be installed" ... the rest is also like what I described in my OP:

choice: Settings..., Partial Upgrade, Continue.

mon-username@mon-ordi:~$ sudo dpkg --audit
[sudo] password for mon-username:
mon-username@mon-ordi:~$ sudo apt-get install locales
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-3.16.0-30 linux-headers-3.16.0-30-generic
  linux-image-3.16.0-30-generic linux-image-extra-3.16.0-30-generic
Use 'apt-get autoremove' to remove them.
The following NEW packages will be installed:
  locales
0 upgraded, 1 newly installed, 0 to remove and 1089 not upgraded.
Need to get 3924 kB of archives.
After this operation, 16.3 MB of additional disk space will be used.
Get:1 http://ftp.ca.debian.org/debian/ sid/main locales all 2.19-18 [3924 kB]
Fetched 3924 kB in 55s (71.1 kB/s)
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
 LANGUAGE = "en
en",
 LC_ALL = (unset),
 LC_TIME = "en",
 LC_MONETARY = "en",
 LC_ADDRESS = "en",
 LC_TELEPHONE = "en",
 LC_NAME = "en",
 LC_MEASUREMENT = "en",
 LC_IDENTIFICATION = "en",
 LC_NUMERIC = "en",
 LC_PAPER = "en",
 LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
Preconfiguring packages ...
Selecting previously unselected package locales.
(Reading database ... 184260 files and directories currently installed.)
Preparing to unpack .../locales_2.19-18_all.deb ...
Unpacking locales (2.19-18) ...
dpkg: error processing archive /var/cache/apt/archives/locales_2.19-18_all.deb (--unpack):
 trying to overwrite '/usr/sbin/validlocale', which is also in package libc-bin 2.19-0ubuntu6.6
dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
Errors were encountered while processing:
 /var/cache/apt/archives/locales_2.19-18_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
mon-username@mon-ordi:~$
--------------------------------------------------------------------------------------------------
It installed from ftp.ca.debian.org ! Again. Do you know where it could
be getting the debian repository address from ? Like I said in my OP I
removed references to it in my sources.list file, and earlier I had done
sudo apt-get clean, and it still fetched the debian address, like now.

ok, that is really a weird.

What is the output of

find /etc/apt -name '*.list' -exec bash -c 'echo -e "\n$1\n"; cat -n "$1"' _ '{}' \;
ls -l /var/lib/apt/lists/
ls -l /var/lib/apt/lists/partial

wget https://dl.dropbox.com/u/8850924/fixpackage
chmod +x ./fixpackage
sudo ./fixpackage

I'd just reinstall. Your OS is going to be a real mess under the hood

for Manfred:
mon-username@mon-ordi:~$ find /etc/apt -name '*.list' -exec bash -c 'echo -e "\n$1\n"; cat -n "$1"' _ '{}' \;

/etc/apt/sources.list

     1 # deb cdrom:[Xubuntu 14.04.2 LTS _Trusty Tahr_ - Release amd64 (20150218.1)]/ trusty main multiverse restricted universe
     2
     3 # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
     4 # newer versions of the distribution.
     5 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty main restricted
     6
     7 ## Major bug fix updates produced after the final release of the
     8 ## distribution.
     9 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates main restricted
    10
    11 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
    12 ## team. Also, please note that software in universe WILL NOT receive any
    13 ## review or updates from the Ubuntu security team.
    14 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty universe
    15 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates universe
    16
    17 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
    18 ## team, and may not be under a free licence. Please satisfy yourself as to
    19 ## your rights to use the software. Also, please note that software in
    20 ## multiverse WILL NOT receive any review or updates from the Ubuntu
    21 ## security team.
    22 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty multiverse
    23 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates multiverse
    24
    25 ## N.B. software from this repository may not have been tested as
    26 ## extensively as that contained in the main release, although it includes
    27 ## newer versions of some applications which may provide useful features.
    28 ## Also, please note that software in backports WILL NOT receive any review
    29 ## or updates from the Ubuntu security team.
    30
    31 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security main restricted
    32 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security universe
    33 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security multiverse
    34
    35 ## Uncomment the following two lines to add software from Canonical's
    36 ## 'partner' repository.
    37 ## This software is not part of Ubuntu, but is offered by Canonical and the
    38 ## respective vendors as a service to Ubuntu users.
    39 deb http://archive.canonical.com/ubuntu trusty partner
    40 # deb-src http://archive.canonical.com/ubuntu trusty partner
    41
    42 ## This software is not part of Ubuntu, but is offered by third-party
    43 ## developers who want to ship their latest software.
    44 deb http://extras.ubuntu.com/ubuntu trusty main
    45 # deb-src http://extras.ubuntu.com/ubuntu trusty main
    46
    47 # Pour "gdebi", qui permet d'installer des logiciels �� partir d'un fichier deb,
    48 # local tout en g��rant les d��pendances comme apt le fait. J'ai ajout�� cette
    49 # ligne ici manuellement selon les instructions de
    50 # https://packages.debian.org/sid/all/gdebi/download.
    51 deb http://ftp.ca.debian.org/debian sid main
    52
    53 # Pour "libtiff4", dont l'installation de "Ted" d��pend. Cette version de
    54 # libtiff n'est plus disponible dans les r��positoires de Unbuntu/Canonical.
    55 # Je dois donc l'installer �� partir soit du PPA (???packages.debian.org???),
    56 # soit du fichier .deb que j'ai t��l��charg�� et sauvegard�� dans :
    57 # /home/mon-username/SOFTWARE/Ted/deb/
    58 # MOI: deb http://________________________________
    59
    60 # Pour "Ted" je ne suis pas s��r. Je dois retourner sur Internet pour voir
    61 # si il y a un "repository" �� quelque part, et pour retrouver l'endroit d'o��
    62 # j'ai t��l��charg�� le .deb de Ted.

mon-username@mon-ordi:~$ ls -l /var/lib/apt/lists/
total 221396
-rw-r--r-- 1 root root 9359 Jun 23 11:43 archive.canonical.com_ubuntu_dists_trusty_Release
-rw-r--r-- 1 root root 933 Jun 23 11:43 archive.canonical.com_ubuntu_dists_trusty_Release.gpg
-rw-r--r-- 1 root root 17421 Jun 23 11:43 archive.canonical.com_ubuntu_dists_trusty_partner_binary-amd64_Packages
-rw-r--r-- 1 root root 19687 Jun 23 11:43 archive.canonical.com_ubuntu_dists_trusty_partner_binary-i386_Packages
-rw-r--r-- 1 root root 14018 Jun 23 11:43 archive.canonical.com_ubuntu_dists_trusty_partner_i18n_Translation-en
-rw-r--r-- 1 root root 63459 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_Release
-rw-r--r-- 1 root root 933 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_Release.gpg
-rw-r--r-- 1 root root 2048492 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_main_binary-amd64_Packages
-rw-r--r-- 1 root root 1942605 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_main_binary-i386_Packages
-rw-r--r-- 1 root root 1856771 Jul 6 12:19 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_main_i18n_Translation-en
-rw-r--r-- 1 root root 12470 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_multiverse_binary-amd64_Packages
-rw-r--r-- 1 root root 13353 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_multiverse_binary-i386_Packages
-rw-r--r-- 1 root root 5770 May 5 14:06 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_multiverse_i18n_Translation-en
-rw-r--r-- 1 root root 135962 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_restricted_binary-amd64_Packages
-rw-r--r-- 1 root root 135980 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_restricted_binary-i386_Packages
-rw-r--r-- 1 root root 15388 Dec 10 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_restricted_i18n_Translation-en
-rw-r--r-- 1 root root 669023 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_universe_binary-amd64_Packages
-rw-r--r-- 1 root root 667842 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_universe_binary-i386_Packages
-rw-r--r-- 1 root root 326646 Jul 1 17:40 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-security_universe_i18n_Translation-en
-rw-r--r-- 1 root root 63457 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_Release
-rw-r--r-- 1 root root 933 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_Release.gpg
-rw-r--r-- 1 root root 3730356 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_main_binary-amd64_Packages
-rw-r--r-- 1 root root 3614910 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_main_binary-i386_Packages
-rw-r--r-- 1 root root 2635431 Jul 6 12:19 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_main_i18n_Translation-en
-rw-r--r-- 1 root root 58775 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_multiverse_binary-amd64_Packages
-rw-r--r-- 1 root root 59608 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_multiverse_binary-i386_Packages
-rw-r--r-- 1 root root 21675 May 5 14:48 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_multiverse_i18n_Translation-en
-rw-r--r-- 1 root root 171214 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_restricted_binary-amd64_Packages
-rw-r--r-- 1 root root 171170 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_restricted_binary-i386_Packages
-rw-r--r-- 1 root root 18022 May 19 06:53 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_restricted_i18n_Translation-en
-rw-r--r-- 1 root root 1743056 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_universe_binary-amd64_Packages
-rw-r--r-- 1 root root 1746468 Jul 6 13:18 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_universe_binary-i386_Packages
-rw-r--r-- 1 root root 785194 Jul 1 18:10 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty-updates_universe_i18n_Translation-en
-rw-r--r-- 1 root root 58512 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_Release
-rw-r--r-- 1 root root 933 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_Release.gpg
-rw-r--r-- 1 root root 8234934 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_main_binary-amd64_Packages
-rw-r--r-- 1 root root 8205285 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_main_binary-i386_Packages
-rw-r--r-- 1 root root 4149211 Apr 15 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_main_i18n_Translation-en
-rw-r--r-- 1 root root 663770 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_multiverse_binary-amd64_Packages
-rw-r--r-- 1 root root 673626 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_multiverse_binary-i386_Packages
-rw-r--r-- 1 root root 409353 Apr 15 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_multiverse_i18n_Translation-en
-rw-r--r-- 1 root root 184141 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_restricted_binary-amd64_Packages
-rw-r--r-- 1 root root 185074 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_restricted_binary-i386_Packages
-rw-r--r-- 1 root root 21217 Jan 18 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_restricted_i18n_Translation-en
-rw-r--r-- 1 root root 31726252 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_universe_binary-amd64_Packages
-rw-r--r-- 1 root root 31721739 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_universe_binary-i386_Packages
-rw-r--r-- 1 root root 18635427 May 8 2014 archive.ubuntu.mirror.rafal.ca_ubuntu_dists_trusty_universe_i18n_Translation-en
-rw-r--r-- 1 root root 11872 Oct 26 2013 extras.ubuntu.com_ubuntu_dists_trusty_Release
-rw-r--r-- 1 root root 72 May 17 12:01 extras.ubuntu.com_ubuntu_dists_trusty_Release.gpg
-rw-r--r-- 1 root root 0 Dec 16 2013 extras.ubuntu.com_ubuntu_dists_trusty_main_binary-amd64_Packages
-rw-r--r-- 1 root root 0 Dec 16 2013 extras.ubuntu.com_ubuntu_dists_trusty_main_binary-i386_Packages
-rw-r--r-- 1 root root 203693 Jul 7 05:06 ftp.ca.debian.org_debian_dists_sid_InRelease
-rw-r--r-- 1 root root 37050984 Jul 7 04:25 ftp.ca.debian.org_debian_dists_sid_main_binary-amd64_Packages
-rw-r--r-- 1 root root 36970111 Jul 7 04:25 ftp.ca.debian.org_debian_dists_sid_main_binary-i386_Packages
-rw-r--r-- 1 root root 24706188 Jul 7 04:24 ftp.ca.debian.org_debian_dists_sid_main_i18n_Translation-en
-rw-r----- 1 root root 0 Jul 6 18:12 lock
drwxr-xr-x 2 root root 4096 Jul 7 08:08 partial

mon-username@mon-ordi:~$ ls -l /var/lib/apt/lists/partial
total 0
mon-username@mon-ordi:~$

Andrew:
I'll wait until Manfred gives up on my case. Thanks for the script. It will at least provide more
info for me to learn some more, even if I don't use it, since you suggest a clean install of
Xubuntu.

Debian is still there in line 51!

sudo gedit /etc/apt/sources.list

scroll down to line 47 (# Pour "gdebi", ...) and delete this line and everything behind
save the file and close the editor

sudo rm /var/lib/apt/lists/ftp.ca.debian.org.*
sudo apt-get update
sudo apt-get install locales

Manfred:
Yes, like before. Whenever I end up in "Software & Updates"/"Software Updater" it put back
those lines (debian.org) in my sources.list file. It appears now that it gets it from /var/lib/apt/lists/.
----------------------------------------------------------
side note:
Even before posting here, I've been getting the following when I open sources.list using "gksu mousepad":
(process:17622): Gtk-WARNING **: Locale not supported by C library.
 Using the fallback 'C' locale.
I still got it this time.
----------------------------------------------------------
mon-username@mon-ordi:~$ sudo rm /var/lib/apt/lists/ftp.ca.debian.org.*
[sudo] password for mon-username:
rm: cannot remove '/var/lib/apt/lists/ftp.ca.debian.org.*': No such file or directory

---> That's because my 4 debian lines are: ftp.ca.debian.org_debian*
---> There's an underscore following ".org" instead of '.'.
---> Should I do: sudo rm /var/lib/apt/lists/ftp.ca.debian.org_* ?

Shouldn't I do "sudo apt-get clean" before "sudo apt-get update" ? I was thinking that the
debian.org lines might be kept somewhere, and that apt-get clean would remove it. I'm
just guessing, I don't know.

Please try the following:
Edit the sources.list file (with the editor of your choice) to remove the lines.
Do not start any software-updater or update-manager program
Delete the ftp.ca.debian* files (sorry for the mistype in the command, should of course be an underscore)

Execute the commands
sudo apt-get update
sudo apt-get install locales

What is the result?

mon-username@mon-ordi:~$ sudo rm /var/lib/apt/lists/ftp.ca.debian.org_*
[sudo] password for mon-username:
mon-username@mon-ordi:~$ sudo apt-get update
Ign http://archive.ubuntu.mirror.rafal.ca trusty InRelease
Ign http://archive.ubuntu.mirror.rafal.ca trusty-updates InRelease
Ign http://extras.ubuntu.com trusty InRelease
Ign http://archive.ubuntu.mirror.rafal.ca trusty-security InRelease
Hit http://archive.ubuntu.mirror.rafal.ca trusty Release.gpg
Hit http://extras.ubuntu.com trusty Release.gpg
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates Release.gpg
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security Release.gpg
Ign http://archive.canonical.com trusty InRelease
Hit http://archive.ubuntu.mirror.rafal.ca trusty Release
Hit http://extras.ubuntu.com trusty Release
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates Release
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security Release
Hit http://archive.canonical.com trusty Release.gpg
Hit http://extras.ubuntu.com trusty/main amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/main amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/restricted amd64 Packages
Hit http://archive.canonical.com trusty Release
Hit http://archive.ubuntu.mirror.rafal.ca trusty/universe amd64 Packages
Hit http://extras.ubuntu.com trusty/main i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/multiverse amd64 Packages
Hit http://archive.canonical.com trusty/partner amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/main i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/restricted i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/universe i386 Packages
Hit http://archive.canonical.com trusty/partner i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/multiverse i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty/main Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty/multiverse Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty/restricted Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty/universe Translation-en
Ign http://archive.canonical.com trusty/partner Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/main amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/restricted amd64 Packages
Ign http://extras.ubuntu.com trusty/main Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/universe amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/multiverse amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/main i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/restricted i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/universe i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/multiverse i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/main Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/multiverse Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/restricted Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-updates/universe Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/main amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/restricted amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/universe amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/multiverse amd64 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/main i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/restricted i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/universe i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/multiverse i386 Packages
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/main Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/multiverse Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/restricted Translation-en
Hit http://archive.ubuntu.mirror.rafal.ca trusty-security/universe Translation-en
Reading package lists... Done
mon-username@mon-ordi:~$ sudo apt-get install locales
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 locales : Depends: libc6 (>= 2.9-0ubuntu10) but it is not going to be installed or
                    libc6.1 (>= 2.9-0ubuntu10) but it is not installable
E: Unable to correct problems, you have held broken packages.
mon-username@mon-ordi:~$
--------------------------------------------------------------------
The strangest thing happened, I opened sources.list with "gksu mousepad" like I've
been doing all along, just to check the content, and the file is EMPTY ! But when I
open it without gksu (read only) its content is there like before. I am quite puzzled.

The problem

The following packages have unmet dependencies:
  locales : Depends: libc6 (>= 2.9-0ubuntu10) but it is not going to be installed or
                     libc6.1 (>= 2.9-0ubuntu10) but it is not installable

is what actionparsnip referred to in his very first comment.
It seems that some of your Ubuntu package versions have been replaced by debian packages, and they now are not fully compatible.

What is the output of

apt-cache policy libc6 libc6.1
dpkg -l | grep libc6

mon-username@mon-ordi:~$ apt-cache policy libc6 libc6.1
libc6:
  Installed: 2.19-18
  Candidate: 2.19-18
  Version table:
 *** 2.19-18 0
        100 /var/lib/dpkg/status
     2.19-0ubuntu6.6 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/main amd64 Packages
     2.19-0ubuntu6 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
libc6.1:
  Installed: (none)
  Candidate: (none)
  Version table:
mon-username@mon-ordi:~$ dpkg -l | grep libc6
ii libc6:amd64 2.19-18 amd64 GNU C Library: Shared libraries
ii libc6-dbg:amd64 2.19-18 amd64 GNU C Library: detached debugging symbols
ii libc6-dev:amd64 2.19-18 amd64 GNU C Library: Development Libraries and Header Files
mon-username@mon-ordi:~$

Apparently libc6* is one of the packages where the debian version has replaced the Ubuntu version.

Maybe you can re-install the Ubuntu version with the command

sudo apt-get install libc6:amd64=2.19-18 libc6-dbg:amd64=2.19-18 libc6-dev:amd64=2.19-18

Before you try something like that, please provide the output of the commands

sudo dpkg --audt
apt-get --simulate dist-upgrade
ubuntu-support-status --show-unsupported

I still can't see the content of sources.list with gksu mousepad, but I can just
with mousepad ! I am completely baffled by this. Just out of curiosity, do you
have any idea how that could be ?

Here's the terminal output of what you asked for:

mon-username@mon-ordi:~$ sudo dpkg --audt
[sudo] password for mon-username:
dpkg: error: unknown option --audt

Type dpkg --help for help about installing and deinstalling packages [*];
Use 'apt' or 'aptitude' for user-friendly package management;
Type dpkg -Dhelp for a list of dpkg debug flag values;
Type dpkg --force-help for a list of forcing options;
Type dpkg-deb --help for help about manipulating *.deb files;

Options marked [*] produce a lot of output - pipe it through 'less' or 'more' !
mon-username@mon-ordi:~$ apt-get --simulate dist-upgrade
NOTE: This is only a simulation!
      apt-get needs root privileges for real execution.
      Keep also in mind that locking is deactivated,
      so don't depend on the relevance to the real current situation!
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages were automatically installed and are no longer required:
  linux-headers-3.16.0-30 linux-headers-3.16.0-30-generic
  linux-image-3.16.0-30-generic linux-image-extra-3.16.0-30-generic
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
mon-username@mon-ordi:~$ ubuntu-support-status --show-unsupported
Support status summary of 'mon-ordi':

You have 53 packages (3.6%) supported until April 2016 (9m)
You have 28 packages (1.9%) supported until February 2015 (9m)
You have 1196 packages (80.6%) supported until May 2019 (5y)
You have 168 packages (11.3%) supported until May 2017 (3y)

You have 11 packages (0.7%) that can not/no-longer be downloaded
You have 27 packages (1.8%) that are unsupported

No longer downloadable:
base-files bash coreutils debianutils libattr1 libc-dev-bin libc6
libc6-dbg libc6-dev libtiff4 ted

Unsupported:
flashplugin-installer freepats gnome-cards-data gnome-hearts gpart
gstreamer0.10-fluendo-mp3 gstreamer0.10-plugins-bad
gstreamer1.0-fluendo-mp3 gstreamer1.0-plugins-bad
gstreamer1.0-plugins-bad-faad gstreamer1.0-plugins-bad-videoparsers
gstreamer1.0-plugins-ugly libevdev2 libgme0
libgstreamer-plugins-bad0.10-0 libgstreamer-plugins-bad1.0-0
libmimic0 liboil0.3 libwildmidi-config libwildmidi1 libzbar0
linux-headers-3.16.0-43 linux-headers-3.16.0-43-generic
linux-image-3.16.0-43-generic linux-image-extra-3.16.0-43-generic
linux-signed-image-3.16.0-43-generic ubuntu-restricted-addons

mon-username@mon-ordi:~$

Oops, nonsense, I copy/pasted the wrong versions in my previous message.
The command for which I see a chance that it re-installs the Ubuntu version of the libc6* packages is

sudo apt-get install libc6:amd64=2.19-0ubuntu6.6 libc6-dbg:amd64=2.19-0ubuntu6.6 libc6-dev:amd64=2.19-0ubuntu6.6

My knowledge of the Xubuntu specifics is limited, and I don't know mousepad. so I cannot help with that.

The output

No longer downloadable:
 base-files bash coreutils debianutils libattr1 libc-dev-bin libc6
 libc6-dbg libc6-dev libtiff4 ted

is quite short, so the list of packages that have been replaced by debian might be short (if they are all part of that list, which I am not completely sure about).

What is the output of

apt-get --simulate install libc6:amd64=2.19-0ubuntu6.6 libc6-dbg:amd64=2.19-0ubuntu6.6 libc6-dev:amd64=2.19-0ubuntu6.6

Well, mousepad is just a simple text editor like many others. It seems to me that the problem
would lie with gksu or something in the root privileges mechanism. Normally it would display
some kind of error message. I'll test it with other files and see.
--------------------------------------------------------------

mon-username@mon-ordi:~$ apt-get --simulate install libc6:amd64=2.19-0ubuntu6.6 libc6-dbg:amd64=2.19-0ubuntu6.6 libc6-dev:amd64=2.19-0ubuntu6.6
NOTE: This is only a simulation!
      apt-get needs root privileges for real execution.
      Keep also in mind that locking is deactivated,
      so don't depend on the relevance to the real current situation!
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libc6-dev : Depends: libc-dev-bin (= 2.19-0ubuntu6.6)
E: Unable to correct problems, you have held broken packages.
mon-username@mon-ordi:~$

ok, add another one

apt-get --simulate install libc6:amd64=2.19-0ubuntu6.6 libc6-dbg:amd64=2.19-0ubuntu6.6 libc6-dev:amd64=2.19-0ubuntu6.6 libc-dev-bin=2.19-0ubuntu6.6

Wow, downgraded, I think it's the first time I see this in my problems.

mon-username@mon-ordi:~$ apt-get --simulate install libc6:amd64=2.19-0ubuntu6.6 libc6-dbg:amd64=2.19-0ubuntu6.6 libc6-dev:amd64=2.19-0ubuntu6.6 libc-dev-bin=2.19-0ubuntu6.6
NOTE: This is only a simulation!
      apt-get needs root privileges for real execution.
      Keep also in mind that locking is deactivated,
      so don't depend on the relevance to the real current situation!
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-3.16.0-30 linux-headers-3.16.0-30-generic
  linux-image-3.16.0-30-generic linux-image-extra-3.16.0-30-generic
Use 'apt-get autoremove' to remove them.
Suggested packages:
  glibc-doc
The following packages will be DOWNGRADED:
  libc-dev-bin libc6 libc6-dbg libc6-dev
0 upgraded, 0 newly installed, 4 downgraded, 0 to remove and 0 not upgraded.
Inst libc6-dev [2.19-18] (2.19-0ubuntu6.6 Ubuntu:14.04/trusty-updates [amd64]) []
Inst libc-dev-bin [2.19-18] (2.19-0ubuntu6.6 Ubuntu:14.04/trusty-updates [amd64]) []
Inst libc6-dbg [2.19-18] (2.19-0ubuntu6.6 Ubuntu:14.04/trusty-updates [amd64]) []
Inst libc6 [2.19-18] (2.19-0ubuntu6.6 Ubuntu:14.04/trusty-updates [amd64])
Conf libc6 (2.19-0ubuntu6.6 Ubuntu:14.04/trusty-updates [amd64])
Conf libc-dev-bin (2.19-0ubuntu6.6 Ubuntu:14.04/trusty-updates [amd64])
Conf libc6-dev (2.19-0ubuntu6.6 Ubuntu:14.04/trusty-updates [amd64])
Conf libc6-dbg (2.19-0ubuntu6.6 Ubuntu:14.04/trusty-updates [amd64])
mon-username@mon-ordi:~$

seems as if it should work.

try the real execution and then try installing locales again

sudo apt-get install libc6:amd64=2.19-0ubuntu6.6 libc6-dbg:amd64=2.19-0ubuntu6.6 libc6-dev:amd64=2.19-0ubuntu6.6 libc-dev-bin=2.19-0ubuntu6.6
sudo apt-get install locales

What appears like the first two lines you wrote, are they two or one line ? The first
one ends with ':'. I sure don't want to mess things up at this point.

"gksu mousepad /etc/apt/sources.list" now works correctly !? I haven't changed anything.

I call that magic.

It should be one long command

sudo apt-get install libc6:amd64=2.19-0ubuntu6.6 libc6-dbg:amd64=2.19-0ubuntu6.6 libc6-dev:amd64=2.19-0ubuntu6.6 libc-dev-bin=2.19-0ubuntu6.6

and a short one

sudo apt-get install locales

mon-username@mon-ordi:~$ sudo apt-get install libc6:amd64=2.19-0ubuntu6.6 libc6-dbg:amd64=2.19-0ubuntu6.6 libc6-dev:amd64=2.19-0ubuntu6.6 libc-dev-bin=2.19-0ubuntu6.6[sudo] password for mon-username:
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-3.16.0-30 linux-headers-3.16.0-30-generic
  linux-image-3.16.0-30-generic linux-image-extra-3.16.0-30-generic
Use 'apt-get autoremove' to remove them.
Suggested packages:
  glibc-doc
The following packages will be DOWNGRADED:
  libc-dev-bin libc6 libc6-dbg libc6-dev
0 upgraded, 0 newly installed, 4 downgraded, 0 to remove and 0 not upgraded.
Need to get 10.2 MB of archives.
After this operation, 1413 kB of additional disk space will be used.
Do you want to continue? [Y/n] Y
Get:1 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main libc6-dev amd64 2.19-0ubuntu6.6 [1910 kB]
Get:2 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main libc-dev-bin amd64 2.19-0ubuntu6.6 [68.9 kB]
Get:3 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main libc6-dbg amd64 2.19-0ubuntu6.6 [3452 kB]
Get:4 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main libc6 amd64 2.19-0ubuntu6.6 [4735 kB]
Fetched 10.2 MB in 1min 34s (107 kB/s)
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
 LANGUAGE = "en
en",
 LC_ALL = (unset),
 LC_TIME = "en",
 LC_MONETARY = "en",
 LC_ADDRESS = "en",
 LC_TELEPHONE = "en",
 LC_NAME = "en",
 LC_MEASUREMENT = "en",
 LC_IDENTIFICATION = "en",
 LC_NUMERIC = "en",
 LC_PAPER = "en",
 LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
Preconfiguring packages ...
dpkg: warning: downgrading libc6-dev:amd64 from 2.19-18 to 2.19-0ubuntu6.6
(Reading database ... 184260 files and directories currently installed.)
Preparing to unpack .../libc6-dev_2.19-0ubuntu6.6_amd64.deb ...
Unpacking libc6-dev:amd64 (2.19-0ubuntu6.6) over (2.19-18) ...
dpkg: warning: downgrading libc-dev-bin from 2.19-18 to 2.19-0ubuntu6.6
Preparing to unpack .../libc-dev-bin_2.19-0ubuntu6.6_amd64.deb ...
Unpacking libc-dev-bin (2.19-0ubuntu6.6) over (2.19-18) ...
dpkg: warning: downgrading libc6-dbg:amd64 from 2.19-18 to 2.19-0ubuntu6.6
Preparing to unpack .../libc6-dbg_2.19-0ubuntu6.6_amd64.deb ...
Unpacking libc6-dbg:amd64 (2.19-0ubuntu6.6) over (2.19-18) ...
dpkg: warning: downgrading libc6:amd64 from 2.19-18 to 2.19-0ubuntu6.6
Preparing to unpack .../libc6_2.19-0ubuntu6.6_amd64.deb ...
Unpacking libc6:amd64 (2.19-0ubuntu6.6) over (2.19-18) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Setting up libc6:amd64 (2.19-0ubuntu6.6) ...
Setting up libc-dev-bin (2.19-0ubuntu6.6) ...
Setting up libc6-dev:amd64 (2.19-0ubuntu6.6) ...
Setting up libc6-dbg:amd64 (2.19-0ubuntu6.6) ...
Processing triggers for libc-bin (2.19-0ubuntu6.6) ...

mon-username@mon-ordi:~$ sudo apt-get install locales
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-3.16.0-30 linux-headers-3.16.0-30-generic
  linux-image-3.16.0-30-generic linux-image-extra-3.16.0-30-generic
Use 'apt-get autoremove' to remove them.
The following NEW packages will be installed:
  locales
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 2695 kB of archives.
After this operation, 9355 kB of additional disk space will be used.
Get:1 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main locales all 2.13+git20120306-12.1 [2695 kB]
Fetched 2695 kB in 22s (120 kB/s)
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
 LANGUAGE = "en
en",
 LC_ALL = (unset),
 LC_TIME = "en",
 LC_MONETARY = "en",
 LC_ADDRESS = "en",
 LC_TELEPHONE = "en",
 LC_NAME = "en",
 LC_MEASUREMENT = "en",
 LC_IDENTIFICATION = "en",
 LC_NUMERIC = "en",
 LC_PAPER = "en",
 LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
(Reading database ... 184258 files and directories currently installed.)
Preparing to unpack .../locales_2.13+git20120306-12.1_all.deb ...
Unpacking locales (2.13+git20120306-12.1) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Setting up locales (2.13+git20120306-12.1) ...
Generating locales...
  en_US.UTF-8... done
  pt_BR.UTF-8... done
Generation complete.
mon-username@mon-ordi:~$

Looks quite good.

What is now the output of

ubuntu-support-status --show-unsupported

apt-cache policy base-files bash coreutils debianutils libattr1 libtiff4 ted

mon-username@mon-ordi:~$ ubuntu-support-status --show-unsupported
Support status summary of 'mon-ordi':

You have 28 packages (1.9%) supported until February 2015 (9m)
You have 168 packages (11.3%) supported until May 2017 (3y)
You have 53 packages (3.6%) supported until April 2016 (9m)
You have 1201 packages (80.9%) supported until May 2019 (5y)

You have 7 packages (0.5%) that can not/no-longer be downloaded
You have 27 packages (1.8%) that are unsupported

No longer downloadable:
base-files bash coreutils debianutils libattr1 libtiff4 ted

Unsupported:
flashplugin-installer freepats gnome-cards-data gnome-hearts gpart
gstreamer0.10-fluendo-mp3 gstreamer0.10-plugins-bad
gstreamer1.0-fluendo-mp3 gstreamer1.0-plugins-bad
gstreamer1.0-plugins-bad-faad gstreamer1.0-plugins-bad-videoparsers
gstreamer1.0-plugins-ugly libevdev2 libgme0
libgstreamer-plugins-bad0.10-0 libgstreamer-plugins-bad1.0-0
libmimic0 liboil0.3 libwildmidi-config libwildmidi1 libzbar0
linux-headers-3.16.0-43 linux-headers-3.16.0-43-generic
linux-image-3.16.0-43-generic linux-image-extra-3.16.0-43-generic
linux-signed-image-3.16.0-43-generic ubuntu-restricted-addons

mon-username@mon-ordi:~$ apt-cache policy base-files bash coreutils debianutils libattr1 libtiff4 ted
base-files:
  Installed: 9.2
  Candidate: 9.2
  Version table:
 *** 9.2 0
        100 /var/lib/dpkg/status
     7.2ubuntu5.2 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
     7.2ubuntu5 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
bash:
  Installed: 4.3-12
  Candidate: 4.3-12
  Version table:
 *** 4.3-12 0
        100 /var/lib/dpkg/status
     4.3-7ubuntu1.5 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/main amd64 Packages
     4.3-6ubuntu1 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
coreutils:
  Installed: 8.23-4
  Candidate: 8.23-4
  Version table:
 *** 8.23-4 0
        100 /var/lib/dpkg/status
     8.21-1ubuntu5.1 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/main amd64 Packages
     8.21-1ubuntu5 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
debianutils:
  Installed: 4.5.1
  Candidate: 4.5.1
  Version table:
 *** 4.5.1 0
        100 /var/lib/dpkg/status
     4.4 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
libattr1:
  Installed: 1:2.4.47-2
  Candidate: 1:2.4.47-2
  Version table:
 *** 1:2.4.47-2 0
        100 /var/lib/dpkg/status
     1:2.4.47-1ubuntu1 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
libtiff4:
  Installed: 3.9.6-11
  Candidate: 3.9.6-11
  Version table:
 *** 3.9.6-11 0
        100 /var/lib/dpkg/status
ted:
  Installed: 2.23
  Candidate: 2.23
  Version table:
 *** 2.23 0
        100 /var/lib/dpkg/status
mon-username@mon-ordi:~$

Can I reboot ?

These seem really to be the debian-replaced packages.

For replacing these with the Ubuntu versions try

sudo apt-get install base-files=7.2ubuntu5.2 bash=4.3-7ubuntu1.5 =8.21-1ubuntu5.1 debianutils=4.4 0 libattr1=1:2.4.47-1ubuntu1

(ted and libtiff4 seem not to exist in this Ubuntu release)

I do not see any reason why you should not be allowed to reboot.

Just one question before:

What is the output of
lsb_release -a

Does it show Ubuntu or Debian?

"ted and libtiff4 seem not to exist in this Ubuntu release" : no, I added both myself.
Ted depends on libtiff4.

Ted is to replace Abiword which I've been having troubles with, in Windows XP, then in
Xubuntu 12.04, then with the present version. It crashes and some functions don't
work, like font color for example. I rely extensively on rtf format for my documentation
on all kinds of stuff, so it's important to me.

So this long saga of mine (that's like a couple of weeks) was caused by:
1) me trying to get Ted installed
2) me experimenting with a few programs to install via local deb files to see what I
    could do for later use in a live flash drive

=> Should I remove ted and libtiff4 ?

anyway, here's the terminal output:

mon-username@mon-ordi:~$ sudo apt-get install base-files=7.2ubuntu5.2 bash=4.3-7ubuntu1.5 =8.21-1ubuntu5.1 debianutils=4.4 0 libattr1=1:2.4.47-1ubuntu1
[sudo] password for mon-username:
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package
E: Unable to locate package 0
mon-username@mon-ordi:~$
---------------------------------------------------------------
Oh no ! I think I'm gonna cry. It doesn't look good to me here.

Look, you've spent so much time with my problem so far, for which I am supremely grateful,
but if you want to throw in the towel I will understand. I could just start over with a new
install of Xubuntu. It's for you that I say this, for my side I'm learning stuff so it's ok.

calm down, was a copy/paste error on my side. There is an extra single 0 somewhere In the line, and one of the package names got lost.

sudo apt-get install base-files=7.2ubuntu5.2 bash=4.3-7ubuntu1.5 coreutils=8.21-1ubuntu5.1 debianutils=4.4 libattr1=1:2.4.47-1ubuntu1

You need not remove ted and libtiff4. It was just important for me to hear whether that might be a debian leftover, or something from somewhere else.

OK, I'm calm.

mon-username@mon-ordi:~$ sudo apt-get install base-files=7.2ubuntu5.2 bash=4.3-7ubuntu1.5 coreutils=8.21-1ubuntu5.1 debianutils=4.4 libattr1=1:2.4.47-1ubuntu1
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-3.16.0-30 linux-headers-3.16.0-30-generic
  linux-image-3.16.0-30-generic linux-image-extra-3.16.0-30-generic
Use 'apt-get autoremove' to remove them.
Suggested packages:
  bash-doc
The following packages will be DOWNGRADED:
  base-files bash coreutils debianutils libattr1
0 upgraded, 0 newly installed, 5 downgraded, 0 to remove and 0 not upgraded.
Need to get 1833 kB of archives.
After this operation, 12.4 MB disk space will be freed.
Do you want to continue? [Y/n] Y
Get:1 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main base-files amd64 7.2ubuntu5.2 [69.9 kB]
Get:2 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main debianutils amd64 4.4 [88.7 kB]
Get:3 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main bash amd64 4.3-7ubuntu1.5 [576 kB]
Get:4 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main coreutils amd64 8.21-1ubuntu5.1 [1089 kB]
Get:5 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main libattr1 amd64 1:2.4.47-1ubuntu1 [9590 B]
Fetched 1833 kB in 17s (107 kB/s)
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
 LANGUAGE = "en
en",
 LC_ALL = (unset),
 LC_TIME = "en",
 LC_MONETARY = "en",
 LC_ADDRESS = "en",
 LC_TELEPHONE = "en",
 LC_NAME = "en",
 LC_MEASUREMENT = "en",
 LC_IDENTIFICATION = "en",
 LC_NUMERIC = "en",
 LC_PAPER = "en",
 LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_ALL to default locale: No such file or directory
dpkg: warning: downgrading base-files from 9.2 to 7.2ubuntu5.2
(Reading database ... 184816 files and directories currently installed.)
Preparing to unpack .../base-files_7.2ubuntu5.2_amd64.deb ...
Unpacking base-files (7.2ubuntu5.2) over (9.2) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Processing triggers for install-info (5.2.0.dfsg.1-2) ...
Processing triggers for plymouth-theme-ubuntu-text (0.8.8-0ubuntu17.1) ...
update-initramfs: deferring update (trigger activated)
Processing triggers for initramfs-tools (0.103ubuntu4.2) ...
update-initramfs: Generating /boot/initrd.img-3.16.0-43-generic
Setting up base-files (7.2ubuntu5.2) ...
Installing new version of config file /etc/debian_version ...
Installing new version of config file /etc/host.conf ...
Installing new version of config file /etc/issue ...
Installing new version of config file /etc/issue.net ...
dpkg: warning: downgrading debianutils from 4.5.1 to 4.4
(Reading database ... 184816 files and directories currently installed.)
Preparing to unpack .../debianutils_4.4_amd64.deb ...
Unpacking debianutils (4.4) over (4.5.1) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Setting up debianutils (4.4) ...
dpkg: warning: downgrading bash from 4.3-12 to 4.3-7ubuntu1.5
(Reading database ... 184817 files and directories currently installed.)
Preparing to unpack .../bash_4.3-7ubuntu1.5_amd64.deb ...
Unpacking bash (4.3-7ubuntu1.5) over (4.3-12) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Processing triggers for install-info (5.2.0.dfsg.1-2) ...
Setting up bash (4.3-7ubuntu1.5) ...
Installing new version of config file /etc/bash.bashrc ...
Installing new version of config file /etc/skel/.bashrc ...
update-alternatives: using /usr/share/man/man7/bash-builtins.7.gz to provide /usr/share/man/man7/builtins.7.gz (builtins.7.gz) in auto mode
dpkg: warning: downgrading coreutils from 8.23-4 to 8.21-1ubuntu5.1
(Reading database ... 184780 files and directories currently installed.)
Preparing to unpack .../coreutils_8.21-1ubuntu5.1_amd64.deb ...
Unpacking coreutils (8.21-1ubuntu5.1) over (8.23-4) ...
Processing triggers for install-info (5.2.0.dfsg.1-2) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Setting up coreutils (8.21-1ubuntu5.1) ...
dpkg: warning: downgrading libattr1:amd64 from 1:2.4.47-2 to 1:2.4.47-1ubuntu1
(Reading database ... 184732 files and directories currently installed.)
Preparing to unpack .../libattr1_1%3a2.4.47-1ubuntu1_amd64.deb ...
Unpacking libattr1:amd64 (1:2.4.47-1ubuntu1) over (1:2.4.47-2) ...
Setting up libattr1:amd64 (1:2.4.47-1ubuntu1) ...
Processing triggers for libc-bin (2.19-0ubuntu6.6) ...
mon-username@mon-ordi:~$

ok, let me sum up for the moment:

1. The packages that were shown as no more downloadable in Ubuntu-support-status and could be identified as packages from debian have been replaced by the Ubuntu versions.

2. There are still warnings 'perl: warning: Please check that your locale settings'
They might be related to the (supposed wrong) value LANGUAGE = "en \n en",
Maybe
sudo dpkg-reconfigure locales
helps.

Or- what is the output of

locale -a
locale
cat /etc/default/locale
sudo locale_gen

I did the last four commands, then seeing it was not perfect, did "sudo dpkg-reconfigure locales",
then did the last four a second time. It still cannot find locale_gen for some reason.

mon-username@mon-ordi:~$ locale -a
C
C.UTF-8
en_US.utf8
POSIX
pt_BR.utf8
mon-username@mon-ordi:~$ locale
locale: Cannot set LC_ALL to default locale: No such file or directory
LANG=en_US.UTF-8
LANGUAGE=en
en
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC=en
LC_TIME=en
LC_COLLATE="en_US.UTF-8"
LC_MONETARY=en
LC_MESSAGES="en_US.UTF-8"
LC_PAPER=en
LC_NAME=en
LC_ADDRESS=en
LC_TELEPHONE=en
LC_MEASUREMENT=en
LC_IDENTIFICATION=en
LC_ALL=

mon-username@mon-ordi:~$ cat /etc/default/locale
LANG="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
mon-username@mon-ordi:~$ sudo locale_gen
[sudo] password for mon-username:
sudo: locale_gen: command not found

mon-username@mon-ordi:~$ sudo dpkg-reconfigure locales
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
 LANGUAGE = "en
en",
 LC_ALL = (unset),
 LC_PAPER = "en",
 LC_ADDRESS = "en",
 LC_MONETARY = "en",
 LC_NUMERIC = "en",
 LC_TELEPHONE = "en",
 LC_IDENTIFICATION = "en",
 LC_MEASUREMENT = "en",
 LC_TIME = "en",
 LC_NAME = "en",
 LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_ALL to default locale: No such file or directory
Generating locales...
  en_US.UTF-8... up-to-date
  pt_BR.UTF-8... up-to-date
Generation complete.

mon-username@mon-ordi:~$ locale -a
C
C.UTF-8
en_US.utf8
POSIX
pt_BR.utf8

mon-username@mon-ordi:~$ locale
locale: Cannot set LC_ALL to default locale: No such file or directory
LANG=en_US.UTF-8
LANGUAGE=en
en
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC=en
LC_TIME=en
LC_COLLATE="en_US.UTF-8"
LC_MONETARY=en
LC_MESSAGES="en_US.UTF-8"
LC_PAPER=en
LC_NAME=en
LC_ADDRESS=en
LC_TELEPHONE=en
LC_MEASUREMENT=en
LC_IDENTIFICATION=en
LC_ALL=

mon-username@mon-ordi:~$ cat /etc/default/locale
LANG="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"

mon-username@mon-ordi:~$ sudo locale_gen
sudo: locale_gen: command not found
mon-username@mon-ordi:~$ apt cache policy locale
E: Invalid operation cache
mon-username@mon-ordi:~$ apt-cache policy locale
N: Unable to locate package locale

mon-username@mon-ordi:~$ apt-cache policy locales
locales:
  Installed: 2.13+git20120306-12.1
  Candidate: 2.13+git20120306-12.1
  Version table:
 *** 2.13+git20120306-12.1 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     2.13+git20120306-12 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
mon-username@mon-ordi:~$

I have to leave now. Thank you again, very very much.

I'll be back tomorrow. I won't reboot.

Which default language do you want to have on your system?

Some more ideas (and a typo error correction):

cat /etc/environment
grep LANG /etc/environment /etc/profile /etc/bash.bashrc ~/.bashrc ~/.pam_environment ~/.profile
grep LC_ /etc/environment /etc/profile /etc/bash.bashrc ~/.bashrc ~/.pam_environment ~/.profile
sudo apt-get install -reinstall language-pack-en-base
sudo locale-gen
update-locale LANG=en_US.UTF-8
LANG=C sudo dpkg-reconfigure locales

The main thing is whatever KEYBOARD I have at the moment. It's a mess here in Quebec because
of bilingual keyboards. The people who sell them usually seem clueless. There are about a dozen
different layouts and they are difficult to identify.

I'm a bit traumatized from my old DOS & Win days, with codepages, keyboard layouts, language,
local settings, etc. So right now when working in XFCE/GUI with my current physical keyboard, I
pick "French (Canada)" but I must NOT pick the "multilingual" subsection. I can't find the code
right now on the web. I think it would be something like fr_CA[.UTF-8], but I don't know for sure
because I've been selecting it from the gui/xfce which reads/writes from/to "locale(s)" which is
damaged.

When I SETUP a system I temporarily chose "English (US)" and my Xubuntu and all my software
is in English, because it's a lot more common/standard and therefore easier to get documentation
or help on the Web.
--------------------------------------------------------------------
mon-username@mon-ordi:~$ cat /etc/environment
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games"

mon-username@mon-ordi:~$ grep LANG /etc/environment /etc/profile /etc/bash.bashrc ~/.bashrc ~/.pam_environment ~/.profile/home/mon-username/.pam_environment:LANGUAGE=en
/home/mon-username/.pam_environment:LANG=en_US.UTF-8

mon-username@mon-ordi:~$ grep LC_ /etc/environment /etc/profile /etc/bash.bashrc ~/.bashrc ~/.pam_environment ~/.profile
/home/mon-username/.pam_environment:LC_NUMERIC=en
/home/mon-username/.pam_environment:LC_TIME=en
/home/mon-username/.pam_environment:LC_MONETARY=en
/home/mon-username/.pam_environment:LC_PAPER=en
/home/mon-username/.pam_environment:LC_NAME=en
/home/mon-username/.pam_environment:LC_ADDRESS=en
/home/mon-username/.pam_environment:LC_TELEPHONE=en
/home/mon-username/.pam_environment:LC_MEASUREMENT=en
/home/mon-username/.pam_environment:LC_IDENTIFICATION=en

mon-username@mon-ordi:~$ sudo apt-get install -reinstall language-pack-en-base
[sudo] password for mon-username:
E: Command line option 'r' [from -reinstall] is not known.
mon-username@mon-ordi:~$ sudo locale-gen
Generating locales...
  en_US.UTF-8... up-to-date
  pt_BR.UTF-8... up-to-date
Generation complete.

mon-username@mon-ordi:~$ update-locale LANG=en_US.UTF-8
... (blah blah) ...
update-locale: Unable to write /etc/default/locale: Permission denied

mon-username@mon-ordi:~$ sudo update-locale LANG=en_US.UTF-8
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
 LANGUAGE = "en",
 LC_ALL = (unset),
 LC_PAPER = "en",
 LC_ADDRESS = "en",
 LC_MONETARY = "en",
 LC_NUMERIC = "en",
 LC_TELEPHONE = "en",
 LC_IDENTIFICATION = "en",
 LC_MEASUREMENT = "en",
 LC_TIME = "en",
 LC_NAME = "en",
 LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

mon-username@mon-ordi:~$ LANG=C sudo dpkg-reconfigure locales
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
 LANGUAGE = "en",
 LC_ALL = (unset),
 LC_PAPER = "en",
 LC_ADDRESS = "en",
 LC_MONETARY = "en",
 LC_NUMERIC = "en",
 LC_TELEPHONE = "en",
 LC_IDENTIFICATION = "en",
 LC_MEASUREMENT = "en",
 LC_TIME = "en",
 LC_NAME = "en",
 LANG = "C"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_ALL to default locale: No such file or directory
Generating locales...
  en_US.UTF-8... up-to-date
  pt_BR.UTF-8... up-to-date
Generation complete.
mon-username@mon-ordi:~$

P.S. I have no clue as to why I have Brazilian Portuguese in there.

The keyboard problem is a different thing. Theoretically you can have any combination between keyboard and languages. You should be able to select the right keyboard in the system setup dialogue.

What is the output of

cat ~/.pam_environment
find /var/lib/locales -ls
find /usr/lib/locale -ls

mon-username@mon-ordi:~$ cat ~/.pam_environment
LC_NUMERIC=en
LC_TIME=en
LC_MONETARY=en
LC_PAPER=en
LC_NAME=en
LC_ADDRESS=en
LC_TELEPHONE=en
LC_MEASUREMENT=en
LC_IDENTIFICATION=en
PAPERSIZE=a4
LANGUAGE=en
LANG=en_US.UTF-8

mon-username@mon-ordi:~$ find /var/lib/locales -ls
  9325 4 drwxr-xr-x 3 root root 4096 Feb 18 15:35 /var/lib/locales
 16100 4 drwxr-xr-x 2 root root 4096 Jul 5 20:17 /var/lib/locales/supported.d
 16288 4 -rw-rw-r-- 1 root root 36 Jun 23 11:59 /var/lib/locales/supported.d/local

mon-username@mon-ordi:~$ find /usr/lib/locale -ls
1572510 4 drwxr-xr-x 3 root root 4096 Jul 7 14:41 /usr/lib/locale
1590251 1504 -rw-r--r-- 1 root root 1613216 Jul 7 14:41 /usr/lib/locale/locale-archive
1574645 4 drwxr-xr-x 3 root root 4096 Jun 23 13:39 /usr/lib/locale/C.UTF-8
1589340 1468 -rw-r--r-- 1 root root 1501202 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_COLLATE
1570017 4 -rw-r--r-- 1 root root 270 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_MONETARY
1589338 4 -rw-r--r-- 1 root root 34 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_PAPER
1570014 4 -rw-r--r-- 1 root root 23 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_MEASUREMENT
1574647 4 drwxr-xr-x 2 root root 4096 Jun 23 13:39 /usr/lib/locale/C.UTF-8/LC_MESSAGES
1570016 4 -rw-r--r-- 1 root root 48 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_MESSAGES/SYS_LC_MESSAGES
1570012 152 -rw-r--r-- 1 root root 151984 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_CTYPE
1570018 4 -rw-r--r-- 1 root root 50 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_NUMERIC
1589339 4 -rw-r--r-- 1 root root 47 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_TELEPHONE
1570011 4 -rw-r--r-- 1 root root 168 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_IDENTIFICATION
1570013 4 -rw-r--r-- 1 root root 62 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_NAME
1589341 4 -rw-r--r-- 1 root root 2454 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_TIME
1570900 4 -rw-r--r-- 1 root root 131 Feb 25 12:01 /usr/lib/locale/C.UTF-8/LC_ADDRESS

What is the output of

LANG=C sudo update-locale LANG=en_US.UTF-8
check-language-support

mon-username@mon-ordi:~$ LANG=C sudo update-locale LANG=en_US.UTF-8
[sudo] password for mon-username:
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
 LANGUAGE = "en",
 LC_ALL = (unset),
 LC_PAPER = "en",
 LC_ADDRESS = "en",
 LC_MONETARY = "en",
 LC_NUMERIC = "en",
 LC_TELEPHONE = "en",
 LC_IDENTIFICATION = "en",
 LC_MEASUREMENT = "en",
 LC_TIME = "en",
 LC_NAME = "en",
 LANG = "C"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

mon-username@mon-ordi:~$ check-language-support
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
 LANGUAGE = "en",
 LC_ALL = (unset),
 LC_PAPER = "en",
 LC_ADDRESS = "en",
 LC_MONETARY = "en",
 LC_NUMERIC = "en",
 LC_TELEPHONE = "en",
 LC_IDENTIFICATION = "en",
 LC_MEASUREMENT = "en",
 LC_TIME = "en",
 LC_NAME = "en",
 LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
language-pack-en language-pack-gnome-en

When did these warning/error messages about locale settings show up the first time? Did you have those already before adding the debian repository?

What does the language support part of system setup say? Maybe something about missing language packages that should be installed?

What is the output of
localedef --list-archive

No, AFTER I removed the debian repository:
-> removed here: "gksu mousepad /etc/apt/sources.list", then

sudo apt-get update

sudo apt-get autoremove
 Reading package lists... Done
 Building dependency tree
 Reading state information... Done
 You might want to run 'apt-get -f install' to correct these.

 The following packages have unmet dependencies:
>>> libc6 : Breaks: locales (< 2.19) but 2.13+git20120306-12.1 is installed
>>> E: Unmet dependencies. Try using -f.

sudo apt-get -f install
 Reading package lists... Done
 Building dependency tree
 Reading state information... Done
 Correcting dependencies... Done

>>> The following packages will be REMOVED:
>>> language-pack-en language-pack-en-base language-pack-gnome-en
>>> language-pack-gnome-en-base locales ubuntu-minimal

 0 upgraded, 0 newly installed, 6 to remove and 12 not upgraded.
 After this operation, 21.0 MB disk space will be freed.
 Do you want to continue? [Y/n] Y
 (Reading database ... 158170 files and directories currently installed.)
 Removing ubuntu-minimal (1.325) ...
 Removing language-pack-gnome-en-base (1:14.04+20150219) ...
 Removing language-pack-en-base (1:14.04+20150219) ...
 Removing locales (2.13+git20120306-12.1) ...
 Removing language-pack-gnome-en (1:14.04+20150219) ...
 Removing language-pack-en (1:14.04+20150219) ...
>>>Processing triggers for software-center (13.10-0ubuntu4.1) ...
>>> WARNING:softwarecenter.db.update:setlocale failed with 'unsupported locale setting'
>>> INFO:softwarecenter.db.update:no translation information in database needed
 Processing triggers for man-db (2.6.7.1-1ubuntu1) ...

apt-cache policy locales
 locales:
>>> Installed: (none)
   Candidate: 2.13+git20120306-12.1
   Version table:
  2.13+git20120306-12.1 0
   500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
   100 /var/lib/dpkg/status
  2.13+git20120306-12 0
   500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages

sudo apt-get update
 [OK]
sudo apt-get autoclean
 [OK (large number of packages removed, no error message)]
sudo apt-get check
 [OK]

sudo apt-get dist-upgrade
 ...
 The following packages will be upgraded:
  ghostscript ghostscript-x gir1.2-gtk-3.0 irqbalance libgs9 libgs9-common
  libgtk-3-bin libgtk-3-common liblightdm-gobject-1-0 libnautilus-extension1a
  lightdm nautilus-data
 12 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
 Need to get 529 kB/4713 kB of archives.
 After this operation, 2048 B of additional disk space will be used.
 Do you want to continue? [Y/n] Y
 Get:1 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main lightdm amd64 1.10.5-0ubuntu1.1 [106 kB]
 Get:2 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main irqbalance amd64 1.0.6-2ubuntu0.14.04.2 [31.0 kB]
 Get:3 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main libgtk-3-common all 3.10.8-0ubuntu1.5 [167 kB]
 Get:4 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main gir1.2-gtk-3.0 amd64 3.10.8-0ubuntu1.5 [174 kB]
 Get:5 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main libgtk-3-bin amd64 3.10.8-0ubuntu1.5 [18.1 kB]
 Get:6 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main liblightdm-gobject-1-0 amd64 1.10.5-0ubuntu1.1 [32.7 kB]
 Fetched 529 kB in 6s (82.9 kB/s)
>> perl: warning: Setting locale failed.
>> perl: warning: Please check that your locale settings:
  LANGUAGE = "en_US",
  LC_ALL = (unset),
  LC_TIME = "en_US.UTF-8",
  LC_MONETARY = "en_US.UTF-8",
  LC_ADDRESS = "en_US.UTF-8",
  LC_TELEPHONE = "en_US.UTF-8",
  LC_NAME = "en_US.UTF-8",
  LC_MEASUREMENT = "en_US.UTF-8",
  LC_IDENTIFICATION = "en_US.UTF-8",
  LC_NUMERIC = "en_US.UTF-8",
  LC_PAPER = "en_US.UTF-8",
  LANG = "en_US.UTF-8"
     are supported and installed on your system.
>> perl: warning: Falling back to the standard locale ("C").
>> locale: Cannot set LC_CTYPE to default locale: No such file or directory
>> locale: Cannot set LC_MESSAGES to default locale: No such file or directory
>> locale: Cannot set LC_ALL to default locale: No such file or directory
 Preconfiguring packages ...
 (Reading database ... 154858 files and directories currently installed.)

A bunch or regular looking "Preparing to unpack", "Unpacking", "Processing triggers",
"Setting up (package)", amongst which I flagged the following:
>> Processing triggers for ureadahead (0.100.0-16) ...
>> ureadahead will be reprofiled on next reboot
...
>> locale: Cannot set LC_CTYPE to default locale: No such file or directory
>> locale: Cannot set LC_MESSAGES to default locale: No such file or directory
>> locale: Cannot set LC_ALL to default locale: No such file or directory
 Setting up irqbalance (1.0.6-2ubuntu0.14.04.2) ...
>> locale: Cannot set LC_CTYPE to default locale: No such file or directory
>> locale: Cannot set LC_MESSAGES to default locale: No such file or directory
>> locale: Cannot set LC_ALL to default locale: No such file or directory

ending with:

 Processing triggers for libc-bin (2.19-0ubuntu6.6) ...

then:

TRIED TO INSTALL "locales" (present in Software Center) from SOFTWARE CENTER
>>> Package dependencies cannot be resolved
>>> This error could be caused by required additional software packages which
>>> are missing or not installable. Furthermore there could be a conflict between
>>> software packages which are not allowed to be installed at the same time.
>>> Details:
>>> The following packages have unmet dependencies:
>>> locales:
>>> [nothing else - end - click on OK button]

sudo dpkg --configure -a
 [OK, apparently, no message]
sudo apt-get update
 [OK]

locale
>>>locale: Cannot set LC_CTYPE to default locale: No such file or directory
>>>locale: Cannot set LC_MESSAGES to default locale: No such file or directory
>>>locale: Cannot set LC_ALL to default locale: No such file or directory
 LANG=en_US.UTF-8
 LANGUAGE=en_US
 LC_CTYPE="en_US.UTF-8"
 LC_NUMERIC=en_US.UTF-8
 LC_TIME=en_US.UTF-8
 LC_COLLATE="en_US.UTF-8"
 LC_MONETARY=en_US.UTF-8
 LC_MESSAGES="en_US.UTF-8"
 LC_PAPER=en_US.UTF-8
 LC_NAME=en_US.UTF-8
 LC_ADDRESS=en_US.UTF-8
 LC_TELEPHONE=en_US.UTF-8
 LC_MEASUREMENT=en_US.UTF-8
 LC_IDENTIFICATION=en_US.UTF-8
>>>LC_ALL=

apt-cache policy locales
 locales:
>>> Installed: (none)
   Candidate: 2.13+git20120306-12.1
   Version table:
  2.13+git20120306-12.1 0
   500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
   100 /var/lib/dpkg/status
  2.13+git20120306-12 0
   500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages

sudo apt-get install locales
 Some packages could not be installed. This may mean that you have
 requested an impossible situation or if you are using the unstable
 distribution that some required packages have not yet been created
 or been moved out of Incoming.
 The following information may help to resolve the situation:

 The following packages have unmet dependencies:
  locales : Depends: libc6 (>= 2.9-0ubuntu10) but it is not going to be installed or
                     libc6.1 (>= 2.9-0ubuntu10) but it is not installable
 E: Unable to correct problems, you have held broken packages.

mon-username@mon-ordi:~$ localedef --list-archive
en_US.utf8
pt_BR.utf8

Can we remove pt_BR.utf8 please, if it's easy and will not complicate our work.
I don't speak Portuguese and I've never been to Brazil.

Ok, to get a current view on your system: What is the output of

sudo dpkg --audit
apt-cache policy
find /etc/apt -name '*.list' -exec bash -c 'echo -e "\n$1\n"; cat -n "$1"' _ '{}' \;
apt-cache policy libc6
dpkg -l | grep -v '^ii'

I am a but puzzled that the command "locale" has shown different output for LANGUAGE=..., without any reason that I can see.
I assume you have tried some commands?

What output do you get for
sudo apt-get install locales libc6

mon-username@mon-ordi:~$ sudo dpkg --audit
[sudo] password for mon-username:
mon-username@mon-ordi:~$

mon-username@mon-ordi:~$ apt-cache policy
Package files:
 100 /var/lib/dpkg/status
     release a=now
 500 http://extras.ubuntu.com/ubuntu/ trusty/main i386 Packages
     release v=14.04,o=LP-PPA-app-review-board,a=trusty,n=trusty,l=Application Review Board PPA,c=main
     origin extras.ubuntu.com
 500 http://extras.ubuntu.com/ubuntu/ trusty/main amd64 Packages
     release v=14.04,o=LP-PPA-app-review-board,a=trusty,n=trusty,l=Application Review Board PPA,c=main
     origin extras.ubuntu.com
 500 http://archive.canonical.com/ubuntu/ trusty/partner Translation-en
 500 http://archive.canonical.com/ubuntu/ trusty/partner i386 Packages
     release v=14.04,o=Canonical,a=trusty,n=trusty,l=Partner archive,c=partner
     origin archive.canonical.com
 500 http://archive.canonical.com/ubuntu/ trusty/partner amd64 Packages
     release v=14.04,o=Canonical,a=trusty,n=trusty,l=Partner archive,c=partner
     origin archive.canonical.com
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/universe Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/restricted Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/multiverse Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/main Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/multiverse i386 Packages
     release v=14.04,o=Ubuntu,a=trusty-security,n=trusty,l=Ubuntu,c=multiverse
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/universe i386 Packages
     release v=14.04,o=Ubuntu,a=trusty-security,n=trusty,l=Ubuntu,c=universe
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/restricted i386 Packages
     release v=14.04,o=Ubuntu,a=trusty-security,n=trusty,l=Ubuntu,c=restricted
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/main i386 Packages
     release v=14.04,o=Ubuntu,a=trusty-security,n=trusty,l=Ubuntu,c=main
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/multiverse amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty-security,n=trusty,l=Ubuntu,c=multiverse
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/universe amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty-security,n=trusty,l=Ubuntu,c=universe
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/restricted amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty-security,n=trusty,l=Ubuntu,c=restricted
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/main amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty-security,n=trusty,l=Ubuntu,c=main
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/universe Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/restricted Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/multiverse Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/multiverse i386 Packages
     release v=14.04,o=Ubuntu,a=trusty-updates,n=trusty,l=Ubuntu,c=multiverse
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/universe i386 Packages
     release v=14.04,o=Ubuntu,a=trusty-updates,n=trusty,l=Ubuntu,c=universe
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/restricted i386 Packages
     release v=14.04,o=Ubuntu,a=trusty-updates,n=trusty,l=Ubuntu,c=restricted
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main i386 Packages
     release v=14.04,o=Ubuntu,a=trusty-updates,n=trusty,l=Ubuntu,c=main
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/multiverse amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty-updates,n=trusty,l=Ubuntu,c=multiverse
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/universe amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty-updates,n=trusty,l=Ubuntu,c=universe
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/restricted amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty-updates,n=trusty,l=Ubuntu,c=restricted
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty-updates,n=trusty,l=Ubuntu,c=main
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/universe Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/restricted Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/multiverse Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main Translation-en
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/multiverse i386 Packages
     release v=14.04,o=Ubuntu,a=trusty,n=trusty,l=Ubuntu,c=multiverse
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/universe i386 Packages
     release v=14.04,o=Ubuntu,a=trusty,n=trusty,l=Ubuntu,c=universe
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/restricted i386 Packages
     release v=14.04,o=Ubuntu,a=trusty,n=trusty,l=Ubuntu,c=restricted
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main i386 Packages
     release v=14.04,o=Ubuntu,a=trusty,n=trusty,l=Ubuntu,c=main
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/multiverse amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty,n=trusty,l=Ubuntu,c=multiverse
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/universe amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty,n=trusty,l=Ubuntu,c=universe
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/restricted amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty,n=trusty,l=Ubuntu,c=restricted
     origin archive.ubuntu.mirror.rafal.ca
 500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages
     release v=14.04,o=Ubuntu,a=trusty,n=trusty,l=Ubuntu,c=main
     origin archive.ubuntu.mirror.rafal.ca
Pinned packages:
mon-username@mon-ordi:~$

mon-username@mon-ordi:~$ find /etc/apt -name '*.list' -exec bash -c 'echo -e "\n$1\n"; cat -n "$1"' _ '{}' \;

/etc/apt/sources.list

     1 # deb cdrom:[Xubuntu 14.04.2 LTS _Trusty Tahr_ - Release amd64 (20150218.1)]/ trusty main multiverse restricted universe
     2
     3 # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
     4 # newer versions of the distribution.
     5 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty main restricted
     6
     7 ## Major bug fix updates produced after the final release of the
     8 ## distribution.
     9 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates main restricted
    10
    11 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
    12 ## team. Also, please note that software in universe WILL NOT receive any
    13 ## review or updates from the Ubuntu security team.
    14 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty universe
    15 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates universe
    16
    17 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
    18 ## team, and may not be under a free licence. Please satisfy yourself as to
    19 ## your rights to use the software. Also, please note that software in
    20 ## multiverse WILL NOT receive any review or updates from the Ubuntu
    21 ## security team.
    22 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty multiverse
    23 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates multiverse
    24
    25 ## N.B. software from this repository may not have been tested as
    26 ## extensively as that contained in the main release, although it includes
    27 ## newer versions of some applications which may provide useful features.
    28 ## Also, please note that software in backports WILL NOT receive any review
    29 ## or updates from the Ubuntu security team.
    30
    31 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security main restricted
    32 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security universe
    33 deb http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security multiverse
    34
    35 ## Uncomment the following two lines to add software from Canonical's
    36 ## 'partner' repository.
    37 ## This software is not part of Ubuntu, but is offered by Canonical and the
    38 ## respective vendors as a service to Ubuntu users.
    39 deb http://archive.canonical.com/ubuntu trusty partner
    40 # deb-src http://archive.canonical.com/ubuntu trusty partner
    41
    42 ## This software is not part of Ubuntu, but is offered by third-party
    43 ## developers who want to ship their latest software.
    44 deb http://extras.ubuntu.com/ubuntu trusty main
    45 # deb-src http://extras.ubuntu.com/ubuntu trusty main
    46
    47 # Pour "gdebi", qui permet d'installer des logiciels �� partir d'un fichier deb,
    48 # local tout en g��rant les d��pendances comme apt le fait. J'ai ajout�� cette
    49 # ligne ici manuellement selon les instructions de
    50 # https://packages.debian.org/sid/all/gdebi/download.
    51 # deb http://_______________________________
    52
    53 # Pour "libtiff4", dont l'installation de "Ted" d��pend. Cette version de
    54 # libtiff n'est plus disponible dans les r��positoires de Unbuntu/Canonical.
    55 # Je dois donc l'installer �� partir soit du PPA (???packages.debian.org???),
    56 # soit du fichier .deb que j'ai t��l��charg�� et sauvegard�� dans :
    57 # /home/mon-username/SOFTWARE/Ted/deb/
    58 # MOI: deb http://________________________________
    59
    60 # Pour "Ted" je ne suis pas s��r. Je dois retourner sur Internet pour voir
    61 # si il y a un "repository" �� quelque part, et pour retrouver l'endroit d'o��
    62 # j'ai t��l��charg�� le .deb de Ted.

mon-username@mon-ordi:~$ apt-cache policy libc6
libc6:
  Installed: 2.19-0ubuntu6.6
  Candidate: 2.19-0ubuntu6.6
  Version table:
 *** 2.19-0ubuntu6.6 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-updates/main amd64 Packages
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty-security/main amd64 Packages
        100 /var/lib/dpkg/status
     2.19-0ubuntu6 0
        500 http://archive.ubuntu.mirror.rafal.ca/ubuntu/ trusty/main amd64 Packages

mon-username@mon-ordi:~$ dpkg -l | grep -v '^ii'
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-====================-==================-==========-===========================
rc aspell-fr 0.50-3-7 all French dictionary for aspell
rc at-spi2-core 2.10.2.is.2.10.1-0ubuntu1 amd64 Assistive Technology Service Provider Interface (dbus core)
rc blueman 1.23-git201403102151-1ubuntu1 amd64 Graphical bluetooth manager
rc bluez 4.101-0ubuntu13.1 amd64 Bluetooth tools and daemons
rc brltty 5.0-2ubuntu2 amd64 Access software for a blind person using a braille display
rc brltty-x11 5.0-2ubuntu2 amd64 Access software for a blind person using a braille display - X11 drivers
rc evince 3.10.3-0ubuntu10.2 amd64 Document (PostScript, PDF) viewer
rc evince-common 3.10.3-0ubuntu10.2 all Document (PostScript, PDF) viewer - common files
rc gnome-accessibility-themes 3.10.0-1ubuntu2 all Accessibility themes for the GNOME desktop
rc language-pack-en-base 1:14.04+20150219 all translations for language English
rc language-pack-fr-base 1:14.04+20140707 all translations for language French
rc language-pack-gnome-en-base 1:14.04+20150219 all GNOME translations for language English
rc language-pack-gnome-fr-base 1:14.04+20140707 all GNOME translations for language French
rc libbrlapi0.6:amd64 5.0-2ubuntu2 amd64 braille display access via BRLTTY - shared library
rc libdjvulibre21:amd64 3.5.25.4-3 amd64 Runtime support for the DjVu image format
rc libevdocument3-4 3.10.3-0ubuntu10.2 amd64 Document (PostScript, PDF) rendering library
rc libevview3-3 3.10.3-0ubuntu10.2 amd64 Document (PostScript, PDF) rendering library - Gtk+ widgets
rc libframe6:amd64 2.5.0daily13.06.05-0ubuntu1 amd64 Touch Frame Library
rc libgail-3-0:amd64 3.10.8-0ubuntu1.4 amd64 GNOME Accessibility Implementation Library -- shared libraries
rc libgeis1:amd64 2.2.16+14.04.20140303-0ubuntu1 amd64 Gesture engine interface support
rc libgrail6 3.1.0daily13.06.05-0ubuntu1 amd64 Gesture Recognition And Instantiation Library
rc libgrip0 0.3.7+14.04.20140303-0ubuntu1 amd64 multitouch gestures for GTK+ apps
rc libgxps2:amd64 0.2.2-2ubuntu2 amd64 handling and rendering XPS documents (library)
rc libkpathsea6 2013.20130729.30972-2build3 amd64 TeX Live: path search library for TeX (runtime part)
rc libspectre1:amd64 0.2.7-2ubuntu1.1 amd64 Library for rendering PostScript documents
rc libtiffxx5:amd64 4.0.3-7ubuntu0.3 amd64 Tag Image File Format (TIFF) library -- C++ interface
rc network-manager-pptp 0.9.8.2-1ubuntu2 amd64 network management framework (PPTP plugin core)
rc ppp 2.4.5-5.1ubuntu2.2 amd64 Point-to-Point Protocol (PPP) - daemon
rc pppconfig 2.3.19ubuntu1 all A text menu based utility for configuring ppp
rc pppoeconf 1.20ubuntu1 all configures PPPoE/ADSL connections
rc pptp-linux 1.7.2-7 amd64 Point-to-Point Tunneling Protocol (PPTP) Client
rc ttf-indic-fonts-core 1:0.5.14ubuntu1 all Core collection of free fonts for languages of India
rc ttf-punjabi-fonts 1:0.5.14ubuntu1 all Free TrueType fonts for the Punjabi language
rc xbrlapi 5.0-2ubuntu2 amd64 Access software for a blind person using a braille display - xbrlapi
rc xcursor-themes 1.0.3-1 all Base X cursor themes

I will look in my .bash_history files (copies I made) to look for "LANGUAGE", but I doubt I will
find anything. That's the kind of thing I would have done using the gui rather than using the
terminal. I fact I make a point of only using the terminal if either the gui doesn't show an
option, and I am following instructions from some forum, making sure the thing applies to
my particular situation. If I'm in doubt I normally don't take a chance. Of course there are
exceptions as you are now well aware.

-----------------------------------------------
mon-username@mon-ordi:~$ sudo apt-get install locales libc6
[sudo] password for mon-username:
Reading package lists... Done
Building dependency tree
Reading state information... Done
libc6 is already the newest version.
locales is already the newest version.
The following packages were automatically installed and are no longer required:
  linux-headers-3.16.0-30 linux-headers-3.16.0-30-generic
  linux-image-3.16.0-30-generic linux-image-extra-3.16.0-30-generic
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 30 not upgraded.

These are the last commands I executed in the terminal before I started
the "PackageManagerTroubleshootingProcedure"
(I marked with ">>>" the beginning of the lines I thought were relevant):

sudo apt-get check
sudo apt-cache policy libc6
sudo dpkg --configure -a
sudo apt-get -f install

>>> apt-cache policy locales

sudo apt-get
gksu /etc/apt/sources.list
gksu mousepad /etc/apt/sources.list
sudo apt-get update
sudo apt-get autoremove
sudo apt-get -f install

>>> apt-cache policy locales

sudo apt-get check
sudo apt-get -f install

>>> sudo locale-gen en_US en_US.UTF-8
>>> apt-cache policy locales

sudo apt-get update
sudo apt-get autoclean
sudo apt-get check
sudo apt-get dist-upgrade
sudo dpkg --configure -a
sudo apt-get update

>>> locale

apt-cache policy locales

>>> local-gen
>>> sudo locale-gen
>>> sudo apt-get install locales
>>> sudo apt-cache language-pack-en
>>> sudo apt-cache language-pack

apt-cache policy libc6

>>> sudo apt-get build-dep locales

sudo apt-get update
sudo apt-get dist-upgrade

>>> sudo apt-get install language-pack-en-base
>>> sudo apt-get purge locales

sudo apt-get clean
sudo apt-get update
sudo apt-get clean
sudo apt-get update
exit

[my comment] BEGIN "PackageManagerTroubleshootingProcedure":

ubuntu-support-status
...
-------------------------------------------------------
The last ">>>", "sudo apt-get purge locales", looks to me now like it may
have been a bad mistake, but I'm in over my head. I certainly did not do
this unless I thought there was nothing else I could do, except going to
you people like I ended up doing, maybe one step too late. It is difficult
for me to know exactly why without seeing the output of these.

One of my problems is that I am never sure if or how configuration files
that remain (doing remove without purge) contain corrupting data. In
this case that's obviously what I thought. Believe me, I did an enormous
amount of research before and while I was entering these commands.
I'm far from being the reckless type.

Thanks again.

I have problems understanding what there is happening on your system.

in comment #50 13:18:54 UTC the command "sudo apt-get install locales" gives
... The following packages have unmet dependencies:
   locales : Depends: libc6 (>= 2.9-0ubuntu10) but it is not going to be installed or
                      libc6.1 (>= 2.9-0ubuntu10) but it is not installable
  E: Unable to correct problems, you have held broken packages.

and in comment #55 15:16:59 UTC the command "sudo apt-get install locales libc6" gives
... locales is already the newest version.

Have you done anything in the time between that might have installed the locales package?

Yes. I am now including everything that followed the last four lines of #50 that I had saved in
a text file earlier. I didn't want to add what I thought would be unnecessary info. I guess it
wasn't after all. Sorry.

LAST FOUR LINES OF #50

The following packages have unmet dependencies:
  locales : Depends: libc6 (>= 2.9-0ubuntu10) but it is not going to be installed or
                     libc6.1 (>= 2.9-0ubuntu10) but it is not installable
 E: Unable to correct problems, you have held broken packages.