package fontconfig 2.11.94-0ubuntu1.1 failed to install/upgrade: triggers looping, abandoned

[mihaim]

The problem appeared during upgrading from 16.04 to 18.04
Similar problems were reported, but for upgrade 14.04 to 16.04, so I decided to open a new bug.

The upgrade left the system in a broken state:
root@storage:~# apt update
Hit:1 http://ro.archive.ubuntu.com/ubuntu bionic InRelease
Hit:2 http://ro.archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:3 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:4 http://ro.archive.ubuntu.com/ubuntu bionic-backports InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
2446 packages can be upgraded. Run 'apt list --upgradable' to see them.
root@storage:~# apt upgrade
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:
 audacious : Depends: libaudcore5 (= 3.9-2) but it is not installed
 audacious-plugins : Depends: audacious-plugins-data (= 3.9-1build2) but 3.6.2-2ubuntu1 is installed
                     Depends: libaudcore5 (>= 3.9) but it is not installed
                     Depends: libaudgui5 (>= 3.9) but it is not installed
                     Depends: libaudtag3 (>= 3.8) but it is not installed
                     Depends: libfluidsynth1 (>= 1.1.6-4~) but 1.1.6-3 is installed
 bogofilter-bdb : Depends: libgsl2 but it is not installable
 checkbox-converged : Depends: qtdeclarative5-ubuntu-ui-toolkit-plugin but it is not installable
 debconf : Breaks: update-notifier-common (< 3.187~) but 3.168.9 is installed
 gnupg : Breaks: software-properties-common (<= 0.96.24.3) but 0.96.20.7 is installed
 kdeconnect-plasma : Depends: plasma-workspace but it is not installed
 libavogadro1 : Depends: libglew2.0 (>= 1.12.0) but it is not installed
 libguvcview-1.1-1 : Depends: libgsl2 but it is not installable
 liboxideqtquick0 : Depends: liboxideqtcore0 (= 1.21.5-0ubuntu0.16.04.1) but it is not installable
 libunity-webapps0 : Depends: unity-webapps-service but it is not installable
 mplayer : Depends: libdirectfb-1.7-7 (>= 1.7.7) but it is not installed
 phonon4qt5-backend-gstreamer : Depends: phonon-backend-gstreamer-common (= 4:4.9.0-1) but 4:4.8.2-0ubuntu2 is installed
 software-properties-kde : Depends: python3-pyqt5 but it is not installed
 unity-control-center-signon : Depends: unity-control-center but it is not installed
 unity-webapps-qml : Depends: qtdeclarative5-ubuntu-ui-toolkit-plugin but it is not installable or
                              qtdeclarative5-ubuntu-ui-toolkit-plugin-gles but it is not installable
 update-notifier : Depends: update-notifier-common (= 3.192.1.3) but 3.168.9 is installed
 xaos : Depends: libgsl2 but it is not installable
 xorg : Depends: xserver-xorg (>= 1:7.7+19ubuntu7.1) but 1:7.7+13ubuntu3.1 is installed
E: Unmet dependencies. Try using -f.

Details:

1)
Description: Ubuntu 18.04.1 LTS
Release: 18.04

2)
fontconfig:
  Installed: 2.11.94-0ubuntu1.1
  Candidate: 2.12.6-0ubuntu2
  Version table:
     2.12.6-0ubuntu2 500
        500 http://ro.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
 *** 2.11.94-0ubuntu1.1 100
        100 /var/lib/dpkg/status

3)
I expected a successful upgrade from 16.04 to 18.04

4)
Now I have a broken system :)

ProblemType: Package
DistroRelease: Ubuntu 18.04
Package: fontconfig 2.11.94-0ubuntu1.1
ProcVersionSignature: Ubuntu 4.4.0-131.157-generic 4.4.134
Uname: Linux 4.4.0-131-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
Date: Wed Sep 5 22:11:25 2018
ErrorMessage: triggers looping, abandoned
RelatedPackageVersions:
 dpkg 1.19.0.5ubuntu2
 apt 1.2.27
SourcePackage: fontconfig
Title: package fontconfig 2.11.94-0ubuntu1.1 failed to install/upgrade: triggers looping, abandoned
UpgradeStatus: Upgraded to bionic on 2018-09-05 (0 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.