[Bug 1899000] Re: Upgrade 18.04 --> 20.04 fails

[Brian Murray]

Reviewing the files from your upgrade attempt you seem to have enabled a
PPA that provides sane packages. This will prevent the upgrade as that
PPA contains package version numbers greater than the release to which
you are upgrading. You can revert the PPA by installing the ppa-purge
package from the official Ubuntu archive and then running 'sudo ppa-
purge ppa:sane-project/sane-git' or 'sudo ppa-purge ppa:sane-project
/sane-release' . After that you can try upgrading again and if it still
fails open a new bug report. Thanks and good luck!

** Summary changed:

- Upgrade 18.04 --> 20.04 fails
+ Upgrade 18.04 --> 20.04 fails if using a PPA providing sane packages

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https://bugs.launchpad.net/bugs/1899000

Title:
  Upgrade 18.04 --> 20.04 fails if using a PPA providing sane packages

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

Bug description:
  "lsb_release -rd" reads:
  Description:	Ubuntu 18.04.5 LTS
  Release:	18.04

  Expected behaviour: Perform the dist upgrade

  What happened: Upgrade fails, /var/log/dist-upgrade/main.log end with

  ...
  2020-10-08 10:45:24,510 DEBUG Removing 'python-minimal' (python-is-python2 is being installed on the system)
  2020-10-08 10:45:24,510 INFO failed to remove python-minimal
  2020-10-08 10:45:44,535 ERROR Dist-upgrade failed: 'E:Fehler: Unterbrechungen durch pkgProblemResolver::Resolve hervorgerufen; dies könnte durch zurück
  gehaltene Pakete verursacht worden sein.
  ...

  No glue if this is the very reason or simply non sense...

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: ubuntu-release-upgrader-core 1:18.04.38
  ProcVersionSignature: Ubuntu 4.15.0-118.119-generic 4.15.18
  Uname: Linux 4.15.0-118-generic x86_64
  NonfreeKernelModules: nvidia_modeset nvidia
  ApportVersion: 2.20.9-0ubuntu7.18
  Architecture: amd64
  CrashDB: ubuntu
  Date: Thu Oct  8 10:45:42 2020
  InstallationDate: Installed on 2017-02-04 (1341 days ago)
  InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
  PackageArchitecture: all
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   LANG=de_DE.UTF-8
   SHELL=/bin/bash
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to bionic on 2020-10-08 (0 days ago)
  VarLogDistupgradeTermlog:

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