[Bug 1897781] Re: System upgrade from Ubuntu 18.04 to 20.04 stops part-way through.

[Brian Murray]

It is not enough to uncheck the PPAs in your upgrade sources as that
leaves the packages installed on your system. The libsane packages from
the SANE ppa are causing your failure to upgrade. You'll want to re-
enable the sources and then use the package ppa-purge to restore the
official Ubuntu package versions and disable the PPAs. After that the
upgrade should be calculatable.

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https://bugs.launchpad.net/bugs/1897781

Title:
  System upgrade from Ubuntu 18.04 to 20.04 stops part-way through.

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

Bug description:
  "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'."

  I did uncheck my two ppa in my upgrade sources but still get the above
  error message.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: ubuntu-release-upgrader-core 1:18.04.38
  ProcVersionSignature: Ubuntu 5.4.0-48.52~18.04.1-generic 5.4.60
  Uname: Linux 5.4.0-48-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.17
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: ubuntu:GNOME
  Date: Tue Sep 29 14:33:52 2020
  InstallationDate: Installed on 2020-09-04 (25 days ago)
  InstallationMedia: Ubuntu 18.04.5 LTS "Bionic Beaver" - Release amd64 (20200806.1)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to bionic on 2020-09-29 (0 days ago)
  VarLogDistupgradeTermlog:

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