package python3 3.6.7-1~18.04 failed to install/upgrade: installed python3 package post-installation script subprocess returned error exit status 4

[andrego]

installation or removal of the package failed

ProblemType: Package
DistroRelease: Ubuntu 18.04
Package: python3 3.6.7-1~18.04
ProcVersionSignature: Ubuntu 4.15.0-39.42-generic 4.15.18
Uname: Linux 4.15.0-39-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
Date: Wed Nov 21 11:51:47 2018
ErrorMessage: installed python3 package post-installation script subprocess returned error exit status 4
InstallationDate: Installed on 2018-07-17 (126 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
Python3Details: /usr/bin/python3.6, Python 3.6.7, python3-minimal, 3.6.7-1~18.04
PythonDetails: /usr/bin/python2.7, Python 2.7.15rc1, python-minimal, 2.7.15~rc1-1
RelatedPackageVersions:
 dpkg 1.19.0.5ubuntu2.1
 apt 1.6.6
SourcePackage: python3-defaults
Title: package python3 3.6.7-1~18.04 failed to install/upgrade: installed python3 package post-installation script subprocess returned error exit status 4
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

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

[Matthias Klose (doko)]

this seems to be a gdebi bug. bad package? maybe re-installation helps

Setting up python3 (3.6.7-1~18.04) ...
running python rtupdate hooks for python3.6...
dpkg-query: package 'gdebi-core' is not installed
Use dpkg --info (= dpkg-deb --info) to examine archive files,
and dpkg --contents (= dpkg-deb --contents) to list their contents.
Traceback (most recent call last):
  File "/usr/bin/py3clean", line 210, in <module>
    main()
  File "/usr/bin/py3clean", line 196, in main
    pfiles = set(dpf.from_package(options.package))
  File "/usr/share/python3/debpython/files.py", line 53, in from_package
    raise Exception("cannot get content of %s" % package_name)
Exception: cannot get content of gdebi-core
error running python rtupdate hook gdebi-core
dpkg: error processing package python3 (--configure):
 installed python3 package post-installation script subprocess returned error exit status 4