package python3 3.6.5-3ubuntu1 failed to install/upgrade: installed python3 package post-installation script subprocess returned error exit status 4

[David Parker]

I run 4.15.0-24-generic.
I ran sudo apt-get upgrade

Errors were encountered while processing:
 python3
 update-notifier-common
 python3-update-manager
 update-notifier
 unattended-upgrades
 update-manager
 gnome-menus
 python3-gst-1.0
 networkd-dispatcher
 ufw
 update-manager-core
 gconf2
E: Sub-process /usr/bin/dpkg returned an error code (1)

ProblemType: Package
DistroRelease: Ubuntu 18.04
Package: python3 3.6.5-3ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-24.26-generic 4.15.18
Uname: Linux 4.15.0-24-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
Date: Thu Jul 12 14:01:46 2018
ErrorMessage: installed python3 package post-installation script subprocess returned error exit status 4
Python3Details: /usr/bin/python3.6, Python 3.6.5, python3-minimal, 3.6.5-3ubuntu1
PythonDetails: /usr/bin/python2.7, Python 2.7.15rc1, python-minimal, 2.7.15~rc1-1
RelatedPackageVersions:
 dpkg 1.19.0.5ubuntu2
 apt 1.6.2
SourcePackage: python3-defaults
Title: package python3 3.6.5-3ubuntu1 failed to install/upgrade: installed python3 package post-installation script subprocess returned error exit status 4
UpgradeStatus: Upgraded to bionic on 2018-05-18 (54 days ago)

[Apport retracing service (apport)]

Thank you for taking the time to report this crash and helping to make this software better. This particular crash has already been reported and is a duplicate of bug #1779237, so is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.