can't install hp-plugin (binary plugin) for HP-Laserjet P1007 under fresh install of Ubuntu 18.04.3

A fresh install of ubuntu 18.04.3 didn't allow printing to occur.

the printer is HP Laserjet P1007, connected by USB cable. All hardware works fine.

HPLIP is installed (3.16.10 is what comes with the ubuntu distro by default I think).

I could not get the various utilities such as hp-setup or hp-plugin to work properly - they all fail.

So I downloaded the latest HPLIP - 3.18. Installed this OK. It overrides the existing 3.16.

However this version also wants me to install a binary plugin for the printer. When I run hp-plugin, it goes through the motions until it tries to do the actual install. At that point it gives a message of failure:

Plugin installation failed
error: Python gobject/dbus may be not installed
error: Plug-in install failed.c

If I run hp-check, there is no problem except that it reports that the plugin needs to be installed. The actual result is as follows:

=======================================================================

installer@HAUT-405:~$ hp-check -t
Saving output in log file: /home/installer/hp-check.log

HP Linux Imaging and Printing System (ver. 3.19.11)
Dependency/Version Check Utility ver. 15.1

Copyright (c) 2001-18 HP Development Company, LP
This software comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to distribute it
under certain conditions. See COPYING file for more details.

Note: hp-check can be run in three modes:
1. Compile-time check mode (-c or --compile): Use this mode before compiling the
HPLIP supplied tarball (.tar.gz or .run) to determine if the proper dependencies
are installed to successfully compile HPLIP.
2. Run-time check mode (-r or --run): Use this mode to determine if a distro
supplied package (.deb, .rpm, etc) or an already built HPLIP supplied tarball
has the proper dependencies installed to successfully run.
3. Both compile- and run-time check mode (-b or --both) (Default): This mode
will check both of the above cases (both compile- and run-time dependencies).

Check types:
a. EXTERNALDEP - External Dependencies
b. GENERALDEP - General Dependencies (required both at compile and run time)
c. COMPILEDEP - Compile time Dependencies
d. [All are run-time checks]
PYEXT SCANCONF QUEUES PERMISSION

Status Types:
    OK
    MISSING - Missing Dependency or Permission or Plug-in
    INCOMPAT - Incompatible dependency-version or Plugin-version

---------------
| SYSTEM INFO |
---------------

 Kernel: 5.0.0-36-generic #39~18.04.1-Ubuntu SMP Tue Nov 12 11:09:50 UTC 2019 GNU/Linux
 Host: HAUT-405
 Proc: 5.0.0-36-generic #39~18.04.1-Ubuntu SMP Tue Nov 12 11:09:50 UTC 2019 GNU/Linux
 Distribution: 12 18.04
 Bitness: 64 bit

-----------------------
| HPLIP CONFIGURATION |
-----------------------

HPLIP-Version: HPLIP 3.19.11
HPLIP-Home: /usr/share/hplip
HPLIP-Installation: Auto installation is supported for ubuntu distro 18.04 version

Current contents of '/etc/hp/hplip.conf' file:
# hplip.conf. Generated from hplip.conf.in by configure.

[hplip]
version=3.19.11

[dirs]
home=/usr/share/hplip
run=/var/run
ppd=/usr/share/ppd/HP
ppdbase=/usr/share/ppd
doc=/usr/share/doc/hplip-3.19.11
html=/usr/share/doc/hplip-3.19.11
icon=/usr/share/applications
cupsbackend=/usr/lib/cups/backend
cupsfilter=/usr/lib/cups/filter
drv=/usr/share/cups/drv/hp
bin=/usr/bin
apparmor=/etc/apparmor.d
# Following values are determined at configure time and cannot be changed.
[configure]
network-build=yes
libusb01-build=no
pp-build=no
gui-build=yes
scanner-build=yes
fax-build=yes
dbus-build=yes
cups11-build=no
doc-build=yes
shadow-build=no
hpijs-install=no
foomatic-drv-install=no
foomatic-ppd-install=no
foomatic-rip-hplip-install=no
hpcups-install=yes
cups-drv-install=yes
cups-ppd-install=no
internal-tag=3.19.11
restricted-build=no
ui-toolkit=qt4
qt3=no
qt4=yes
qt5=no
policy-kit=no
lite-build=no
udev_sysfs_rules=no
hpcups-only-build=no
hpijs-only-build=no
apparmor_build=yes
class-driver=no

Current contents of '/var/lib/hp/hplip.state' file:
Plugins are not installed. Could not access file: No such file or directory

Current contents of '~/.hplip/hplip.conf' file:
[upgrade]
notify_upgrade = true
last_upgraded_time = 1575279269
pending_upgrade_time = 0
latest_available_version = 3.17.10

[settings]
systray_visible = 0
systray_messages = 0

[last_used]
device_uri = "hp:/usb/HP_LaserJet_P1007?serial=NC12917"
printer_name =
working_dir = /home/installer/Downloads/hplip-3.19.11-plugin.run

[commands]
scan = /usr/bin/xsane -V %SANE_URI%

[refresh]
rate = 30
enable = false
type = 1

[polling]
enable = false
interval = 5
device_list =

[fax]
voice_phone =
email_address =

[installation]
date_time = 12/02/19 19:49:06
version = 3.19.11

 <Package-name> <Package-Desc> <Required/Optional> <Min-Version> <Installed-Version> <Status> <Comment>

-------------------------
| External Dependencies |
-------------------------

 cups CUPS - Common Unix Printing System REQUIRED 1.1 2.2.7 OK 'CUPS Scheduler is running'
 gs GhostScript - PostScript and PDF language interpreter and previewer REQUIRED 7.05 9.26 OK -
 xsane xsane - Graphical scanner frontend for SANE OPTIONAL 0.9 0.999 OK -
 scanimage scanimage - Shell scanning program OPTIONAL 1.0 1.0.27 OK -
 dbus DBus - Message bus system REQUIRED - 1.12.2 OK -
 policykit PolicyKit - Administrative policy framework OPTIONAL - 0.105 OK -
 network network -wget OPTIONAL - 1.19.4 OK -
 avahi-utils avahi-utils OPTIONAL - 0.7 OK -

------------------------
| General Dependencies |
------------------------

 libjpeg libjpeg - JPEG library REQUIRED - - OK -
 cups-devel CUPS devel- Common Unix Printing System development files REQUIRED - 2.2.7 OK -
 cups-image CUPS image - CUPS image development files REQUIRED - 2.2.7 OK -
 libpthread libpthread - POSIX threads library REQUIRED - b'2.27' OK -
 libusb libusb - USB library REQUIRED - 1.0 OK -
 sane SANE - Scanning library REQUIRED - - OK -
 sane-devel SANE - Scanning library development files REQUIRED - - OK -
 libnetsnmp-devel libnetsnmp-devel - SNMP networking library development files REQUIRED 5.0.9 5.7.3 OK -
 libcrypto libcrypto - OpenSSL cryptographic library REQUIRED - 1.1.1 OK -
 python3X Python 2.2 or greater - Python programming language REQUIRED 2.2 3.6.9 OK -
 python3-notify2 Python libnotify - Python bindings for the libnotify Desktop notifications OPTIONAL - - OK -
 python3-pyqt4-dbus PyQt 4 DBus - DBus Support for PyQt4 OPTIONAL 4.0 4.12.1 OK -
 python3-pyqt4 PyQt 4- Qt interface for Python (for Qt version 4.x) REQUIRED 4.0 4.12.1 OK -
 python3-dbus Python DBus - Python bindings for DBus REQUIRED 0.80.0 1.2.6 OK -
 python3-xml Python XML libraries REQUIRED - 2.2.5 OK -
 python3-devel Python devel - Python development files REQUIRED 2.2 3.6.9 OK -
 python3-pil PIL - Python Imaging Library (required for commandline scanning with hp-scan) OPTIONAL - 6.2.1 OK -
 python3-reportlab Reportlab - PDF library for Python OPTIONAL 2.0 3.4.0 OK -

--------------
| COMPILEDEP |
--------------

 libtool libtool - Library building support services REQUIRED - 2.4.6 OK -
 gcc gcc - GNU Project C and C++ Compiler REQUIRED - 7.4.0 OK -
 make make - GNU make utility to maintain groups of programs REQUIRED 3.0 4.1 OK -

---------------------
| Python Extentions |
---------------------

 cupsext CUPS-Extension REQUIRED - 3.19.11 OK -
 hpmudext IO-Extension REQUIRED - 3.19.11 OK -

----------------------
| Scan Configuration |
----------------------

 hpaio HPLIP-SANE-Backend REQUIRED - 3.19.11 OK 'hpaio found in /etc/sane.d/dll.conf'
 scanext Scan-SANE-Extension REQUIRED - 3.19.11 OK -

------------------------------
| DISCOVERED SCANNER DEVICES |
------------------------------

No Scanner found.

--------------------------
| DISCOVERED USB DEVICES |
--------------------------

  Device URI Model
  -------------------------------- -----------------
  hp:/usb/HP_LaserJet_P1007?serial HP LaserJet P1007
  =NC12917

---------------------------------
| INSTALLED CUPS PRINTER QUEUES |
---------------------------------

HP-LaserJet-P1007
-----------------
Type: Printer
Device URI: hp:/usb/HP_LaserJet_P1007?serial=NC12917
PPD: /etc/cups/ppd/HP-LaserJet-P1007.ppd
PPD Description: HP LaserJet P1007 Foomatic/foo2xqx (recommended)
Printer status: printer HP-LaserJet-P1007 is idle. enabled since Mon 02 Dec 2019 18:20:05 CST
error: Required plug-in status: Not installed
Communication status: Good

--------------
| PERMISSION |
--------------

USB HP-LaserJet-P1007 Required - - OK Node:'/dev/bus/usb/001/004' Perm:' root lp rw- rw- rw- rw- r--'

-----------
| SUMMARY |
-----------

Missing Required Dependencies
-----------------------------
None

Missing Optional Dependencies
-----------------------------
None

Plug-in Status
--------------
error: Plug-ins need to be installed

Total Errors: 1
Total Warnings: 0

Done.

==========================================================

So at this point, not sure what to do.

Does anybody know why hp-plugin fails, with the message that I get (python gobject/dbus not installed)?

Kind regards,

F.