[Bug 1924951] Re: Cannot upgrade from 18.04 to 20.04 "An unresolvable problem occured while calculating the upgrade."

[Brian Murray]

The dialog which follows is the final question before the upgrade
actually begins. If you choose N here your system will be restored to
its previous state.

Calculating the changes

Do you want to start the upgrade?


3 installed packages are no longer supported by Canonical. You can 
still get support from the community. 

16 packages are going to be removed. 322 new packages are going to be 
installed. 1391 packages are going to be upgraded. 

You have to download a total of 1,156 M. This download will take 
about 2 minutes with your connection. 

Installing the upgrade can take several hours. Once the download has 
finished, the process cannot be canceled. 

 Continue [yN]  Details [d]

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https://bugs.launchpad.net/bugs/1924951

Title:
  Cannot upgrade from 18.04 to 20.04 "An unresolvable problem occured
  while calculating the upgrade."

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

Bug description:
  Description:	Ubuntu 18.04.5 LTS
  Release:	18.04

  I clicked the button to upgrade the system in the dialogue box that
  popped up telling me that there is a new version of the OS I can
  upgrade to.

  After the Distribution upgrade was running for a short while, it
  showed the following error message:

  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'.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: ubuntu-release-upgrader-core 1:18.04.42
  ProcVersionSignature: Ubuntu 5.4.0-62.70~18.04.1-generic 5.4.78
  Uname: Linux 5.4.0-62-generic x86_64
  NonfreeKernelModules: nvidia_modeset nvidia
  ApportVersion: 2.20.9-0ubuntu7.21
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: ubuntu:GNOME
  Date: Mon Apr 19 10:28:34 2021
  InstallationDate: Installed on 2019-09-17 (579 days ago)
  InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to bionic on 2021-04-19 (0 days ago)
  VarLogDistupgradeTermlog:

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