package libglib2.0-cil 2.12.40-3 failed to install/upgrade: installed libglib2.0-cil package post-installation script subprocess returned error exit status 1

[Sarah Chatelain]

...

ProblemType: Package
DistroRelease: Ubuntu 20.04
Package: libglib2.0-cil 2.12.40-3
ProcVersionSignature: Ubuntu 5.4.0-48.52-generic 5.4.60
Uname: Linux 5.4.0-48-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.9
Architecture: amd64
CasperMD5CheckResult: skip
Date: Mon Oct 12 09:13:09 2020
ErrorMessage: installed libglib2.0-cil package post-installation script subprocess returned error exit status 1
InstallationDate: Installed on 2018-07-26 (809 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
Python3Details: /usr/bin/python3.8, Python 3.8.5, python3-minimal, 3.8.2-0ubuntu2
PythonDetails: /usr/bin/python2.7, Python 2.7.18, python-is-python2, 2.7.17-4
RelatedPackageVersions:
 dpkg 1.19.7ubuntu3
 apt 2.0.2ubuntu0.1
SourcePackage: gtk-sharp2
Title: package libglib2.0-cil 2.12.40-3 failed to install/upgrade: installed libglib2.0-cil package post-installation script subprocess returned error exit status 1
UpgradeStatus: Upgraded to focal on 2020-10-12 (0 days ago)

[Launchpad Janitor (janitor)]

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

[Sebastien Bacher (seb128)]

Unhandled Exception:
System.TypeInitializationException: The type initializer for 'Sys' threw an exception. ---> System.DllNotFoundException: System.Native assembly:<unknown assembly> type:<unknown type> member:(null)

[Olav Kvittem (okvittem)]

happened during dorelease-upgrade from 18.04 to 20.04
Could not install the upgrades

The upgrade has aborted. Your system could be in an unusable state. A
recovery will run now (dpkg --configure -a).

Setting up libglib2.0-cil (2.12.40-3) ...
* Installing 1 assembly from libglib2.0-cil into Mono
Setting up libglib2.0-cil-dev (2.12.40-3) ...