package update-notifier-common 3.168.10 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[João Luís Monteiro Tavares]

I got this error when trying to update the package update notifier.

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: update-notifier-common 3.168.10
ProcVersionSignature: Ubuntu 4.15.0-66.75~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-66-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.21
Architecture: amd64
Date: Wed Feb 26 11:27:46 2020
DpkgHistoryLog:
 Start-Date: 2020-02-26 11:27:28
 Commandline: apt-get install aptitude
 Requested-By: devugees (1000)
 Install: aptitude-common:amd64 (0.7.4-2ubuntu2, automatic), libcwidget3v5:amd64 (0.5.17-4ubuntu2, automatic), aptitude:amd64 (0.7.4-2ubuntu2)
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2018-03-09 (718 days ago)
InstallationMedia: Ubuntu 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228)
PackageArchitecture: all
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.6
 apt 1.2.32
SourcePackage: update-notifier
Title: package update-notifier-common 3.168.10 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.apt.apt.conf.d.10periodic:
 APT::Periodic::Update-Package-Lists "1";
 APT::Periodic::Download-Upgradeable-Packages "1";
 APT::Periodic::AutocleanInterval "0";
 APT::Periodic::Unattended-Upgrade "0";
mtime.conffile..etc.apt.apt.conf.d.10periodic: 2019-02-08T01:53:45.023772

[Steve Langasek (vorlon)]

The error in your log is:

Traceback (most recent call last):
  File "/usr/lib/update-notifier/package-data-downloader", line 24, in <module>
    import debian.deb822
  File "/usr/lib/python3/dist-packages/debian/deb822.py", line 38, in <module>
    import chardet
ImportError: No module named 'chardet'

Why is your python3 installation broken? Your system has python3-chardet 2.3.0-2 installed but it can't be found by python.

[Launchpad Janitor (janitor)]

[Expired for update-notifier (Ubuntu) because there has been no activity for 60 days.]