[Bug 1902053] Re: dist upgrade from 18.04 to 20.04 crashes

[Glenn Teachey]

Can confirm this is an issue on the latest cloud image built for Azure as well.
SKU: 

Steps to reproduce:
Deploy image
Run 'apt update'
Run 'apt upgrade'
Perform package updates for 18.04
Perform distribution upgrade

Output:
----------------------------------------
Calculating the changes

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If
you want to investigate this yourself the log files in
'/var/log/dist-upgrade' will contain details about the upgrade.
Specifically, look at 'main.log' and 'apt.log'.


Restoring original system state

Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
=== Command detached from window (Thu Apr 29 15:39:57 2021) ===
=== Command terminated with exit status 1 (Thu Apr 29 15:40:07 2021) ===
----------------------------------------------------------------------------------------------------------


Same output in the logs as already attached, same package as above

We're able to get past this by running 'apt purge libpython-stdlib'.
-----------------------------------------------------------------------
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following package was automatically installed and is no longer required:
  linux-headers-4.15.0-142
Use 'sudo apt autoremove' to remove it.
The following packages will be REMOVED:
  libpython-stdlib* python* python-crypto* python-ldb* python-parted* python-samba* python-six* python-tdb* samba-common-bin*
0 upgraded, 0 newly installed, 9 to remove and 0 not upgraded.
After this operation, 18.9 MB disk space will be freed.
Do you want to continue? [Y/n] Y
(Reading database ... 87005 files and directories currently installed.)
Removing samba-common-bin (2:4.7.6+dfsg~ubuntu-0ubuntu2.21) ...
Removing python-samba (2:4.7.6+dfsg~ubuntu-0ubuntu2.21) ...
Removing python-ldb:amd64 (2:1.2.3-1ubuntu0.2) ...
Removing python-parted (3.11.1-1ubuntu2) ...
Removing python-crypto (2.6.1-8ubuntu2) ...
Removing python-six (1.11.0-2) ...
Removing python-tdb (1.3.15-2) ...
Removing python (2.7.15~rc1-1) ...
Removing libpython-stdlib:amd64 (2.7.15~rc1-1) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for libc-bin (2.27-3ubuntu1.4) ...
(Reading database ... 86461 files and directories currently installed.)
Purging configuration files for python (2.7.15~rc1-1) ...
--------------------------------------------------------------------------------------------------------------

Afterwards, the upgrade will complete successfully.

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https://bugs.launchpad.net/bugs/1902053

Title:
  dist upgrade from 18.04 to 20.04 crashes

Status in ubuntu-release-upgrader package in Ubuntu:
  Confirmed

Bug description:
  system is unable to gather needed Information, downloads are working.
  In main.log I found some problem about python:

  .
  .
  .
  2020-10-29 12:04:12,851 INFO removing python-minimal because python-is-python2 is being installed
  2020-10-29 12:04:12,851 DEBUG Removing 'python-minimal' (python-is-python2 is being installed on the system)
  2020-10-29 12:04:12,851 INFO failed to remove python-minimal
  2020-10-29 12:04:12,852 INFO checking for python-dev
  2020-10-29 12:04:12,852 INFO checking for libpython-dev
  2020-10-29 12:04:12,852 INFO checking for libpython-stdlib
  2020-10-29 12:04:12,852 INFO removing libpython-stdlib because None is being installed
  2020-10-29 12:04:12,852 DEBUG Removing 'libpython-stdlib' (None is being installed on the system)
  2020-10-29 12:04:12,852 INFO failed to remove libpython-stdlib
  2020-10-29 12:04:12,852 INFO checking for libpython-dbg
  2020-10-29 12:40:44,140 ERROR Dist-upgrade failed: 'E:Fehler: Unterbrechungen durch pkgProblemResolver::Resolve hervorgerufen; dies könnte durch zurückgehaltene Pakete verursacht worden sein.'
  2020-10-29 12:40:44,141 DEBUG abort called
  2020-10-29 12:40:44,143 DEBUG openCache()
  2020-10-29 12:40:47,859 DEBUG Comparing 5.3.0-62 with 
  2020-10-29 12:40:47,861 DEBUG Comparing 5.4.0-48 with 5.3.0-62
  2020-10-29 12:40:47,861 DEBUG Comparing 5.4.0-51 with 5.4.0-48
  2020-10-29 12:40:47,861 DEBUG Comparing 5.4.0-52 with 5.4.0-51
  2020-10-29 12:40:48,182 DEBUG /openCache(), new cache size 100201

  
  Thank you for your Help,
  J.K.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: ubuntu-release-upgrader-core 1:18.04.40
  ProcVersionSignature: Ubuntu 5.4.0-52.57~18.04.1-generic 5.4.65
  Uname: Linux 5.4.0-52-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.18
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: ubuntu:GNOME
  Date: Thu Oct 29 12:51:07 2020
  InstallationDate: Installed on 2019-04-11 (566 days ago)
  InstallationMedia: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
  PackageArchitecture: all
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=de_DE.UTF-8
   SHELL=/bin/bash
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to bionic on 2020-10-29 (0 days ago)
  VarLogDistupgradeTermlog:

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