Getting annoying message window about authentication

Is there any print queue configured ?
Can you provide us the output of 'lpstat -a'

Sure:

==========================================
kismi@truskawka:~$ lpstat -a
fax accepting requests since czw, 3 wrz 2015, 17:23:14
gabinet1-HP-P1102w accepting requests since pon, 14 wrz 2015, 14:05:31
gabinet2-HP-P1102w accepting requests since pon, 14 wrz 2015, 16:28:00
ksero accepting requests since nie, 14 cze 2015, 20:23:08
Laserjet accepting requests since pon, 14 wrz 2015, 08:14:18
===========================================

gabinet2-HP-P1102w is a local USB printer.
gabinet1-HP-P1102w is a remote CUPS printer
ksero and fax is a network printer (HP directly attached to Ethernet)

This question was expired because it remained in the 'Open' state without activity for the last 15 days.

The problem is still there.
Nobody knows the answer?
Has anyone similar problems?

is your user member of the lp and/or lpadmin groups?

They are members of "lpadmin".

Try adding them to the lp group as well (needs logoff and logon to take effect).

Thanks Manfred for your hint.
Yes, I have added the user to lp group after your first message and re-logged.
We are monitoring the behaviour of the system.
By now the message didn't appear.
I am not sure yet if it is already a success because the message appeared quite randomly with longer and shorter interspace.
I think on Monday evening I would be sure if it is the solution.

It seems to be the correct solution. The message didn't appear any more.
Thanks again, Manfred.

The fanfares were premature. The message appeared again after a few days.
I had no time to get back to it.
Anyone an idea?

Is the user who got the message member of the lp and lpadmin groups?

Yes, she is. Member of both.

What was the action that this person did to receive the message?

Nothing. It appears randomly. I am not able to invoke this message on demand. It is irregular.

Is HPLIP drivers installed in your system ?
can you try configure the print queue using 'hp-setup' command.

We are in hplip thread, so yes, it is installed. With GUI.
Yes, I have used hp-setup to setup the printer.

This question was expired because it remained in the 'Open' state without activity for the last 15 days.

At least I have found some solution.
Stopping CUPS discovery service seems to stop those messages from appearing.
One can do it in a running system:

sudo service cups-browsed stop

or make it permanent (to survive a system restart)

sudo echo manual >/etc/init/cups-browsed.override

This causes that printers in network are not automatically discovered, so you have to define them manually.
Broader description is here http://askubuntu.com/questions/345083/how-do-i-disable-automatic-remote-printer-installation

In the meantime I have also tried to remove hplip-gui, but it doesn't help. The problem seems to be caused by CUPS and not HPLIP.

Another remark is that I have an impression that some unwanted recurrence appears. If you define a remote printer and make it remotely available this may cause recurrence problems. I haven't investigated it further. I have simply noted a 7 times replicated printer in one system. After switching off the CUPS discovery as above they disappeared.

I hope it helps.

Life is cruel.

After some time (over a week) the message reappeared.

So I am still looking for a solution. Any idea?

How does that pop-up look like?

Maybe the following helps to find out the process that is responsible for it:
Whenever that message is shown again, open a terminal window and issue the command
xprop WM_CLASS
The mouse pointer will turn into a cross, and with that cross click on the pop-up message.
After the mouse click, there should be an output I the terminal window telling the name of the program that creates that pup-up.
What is it?

Here is the message: https://drive.google.com/file/d/0B1ZLlrBdpMcSRHZFVVNnU1lLVkE/view?usp=sharing

The problem is it appears randomly. Sometimes several times in a day and sometimes nothing over a week.
I cannot sit there and wait for a week for it to appear. Moreover the computers are intensively used and quite often I cannot disturb them.
Anyway I will try to catch the message.
Looking at the top-left corner it seems it comes from Firefox.

OK, I have the result:

=============
rejestracja@antracyt:~ > xprop WM_CLASS
WM_CLASS(STRING) = "firefox", "Firefox"
=============

As expected - the window comes from Firefox.

I have done some investigation in the meantime.
The cups browser is disabled on the system. So I would expect to see manually configured printers only.
The command "lpc status" shows only "manual" printers (as expected).
Similarly if I try to print from libreoffice only those two printers appear.
But not form firefox. Firefox shows some additional printers as well (cups-provided by other systems).
The question is "How does he know?". Is he doing some network query itself? Or maybe uses some other system like avahi?

This question was expired because it remained in the 'Open' state without activity for the last 15 days.

This is not a final result - I am still testing.
Last time the message reappeared after a week.
But I can describe results of my investigations.

Avahi seems to be good direction.
You can check avahi-discovered resources with:

avahi-browse -t -a

In my case there was plenty of them. The printers among of them. All being provided by IPv4 and IPv6 (so appearing twice).
The service can be configured by editing file "/etc/avahi/avahi-daemon.conf" like:

sudo vi /etc/avahi/avahi-daemon.conf

To activate changes the daemon should be restarted:

sudo service avahi-daemon restart

As I don't use IPv6 I have switched it off introducing a line:

use-ipv6=no

But the most important change I have made was switching the service off on my interface by a line:

deny-interfaces=eth0

With that chance avahi shows no resources any more.
After that change it is over a week now as the message didn't appear.

So as a summary.
Firefox is the guilty one. It should ask only CUPS for list of available printers. It plays clever clever instead and asks (at least) avahi as well. And then shows to an ordinary user a message which is obviously intended for an administrator.
As a workaround I have switched off avahi service.

I will wait (and test the solution) a week more before I announce "Problem Solved" status.

I can just confirm that the message does not appear any more.