package unattended-upgrades 2.3ubuntu0.1 failed to install/upgrade: installed unattended-upgrades package post-installation script subprocess returned error exit status 1

[Suvedha]

This occured while upgrading from Ubuntu 18.04 to 20.04

ProblemType: Package
DistroRelease: Ubuntu 20.04
Package: unattended-upgrades 2.3ubuntu0.1
ProcVersionSignature: Ubuntu 5.4.0-42.46-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.6
Architecture: amd64
CasperMD5CheckResult: skip
Date: Fri Aug 14 16:32:44 2020
ErrorMessage: installed unattended-upgrades package post-installation script subprocess returned error exit status 1
InstallationDate: Installed on 2020-08-07 (7 days ago)
InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
PackageArchitecture: all
Python3Details: /usr/bin/python3.8, Python 3.8.2, python3-minimal, 3.8.2-0ubuntu2
PythonDetails: /usr/bin/python2.7, Python 2.7.18rc1, python-is-python2, 2.7.17-4
RelatedPackageVersions:
 dpkg 1.19.7ubuntu3
 apt 2.0.2ubuntu0.1
SourcePackage: unattended-upgrades
Title: package unattended-upgrades 2.3ubuntu0.1 failed to install/upgrade: installed unattended-upgrades package post-installation script subprocess returned error exit status 1
UpgradeStatus: Upgraded to focal on 2020-08-14 (0 days ago)
modified.conffile..etc.apt.apt.conf.d.10periodic:
 APT::Periodic::Update-Package-Lists "7";
 APT::Periodic::Download-Upgradeable-Packages "0";
 APT::Periodic::AutocleanInterval "0";
 APT::Periodic::Unattended-Upgrade "0";
mtime.conffile..etc.apt.apt.conf.d.10periodic: 2020-08-14T15:42:52.692116

[Balint Reczey (rbalint)]

Seems like the debconf GTK frontend could not find an icon, needs more investigation.