[Bug 1934297] [NEW] upgrade to 20.04 from 18.04 unsuccessful

[Kamikaze Blitzkrieg]

Public bug reported:

(1)Description:	Ubuntu 18.04.5 LTS
Release:	18.04

(2)gnome:
  Installed: (none)
  Candidate: 1:3.22+9
  Version table:
     1:3.22+9 500
        500 http://archive.ubuntu.com/ubuntu bionic/universe amd64 Packages

(3) I expected the upgrade to 20.04 from 18.04 to happen without any issues.
(4) The upgrade failed with this error message. I have also attached the contents of /var/log/dist-upgrade/apt.log and /var/log/dist-upgrade/main.log 


An unresolvable problem occurred while calculating the upgrade.

 This was likely caused by:
 * Unofficial software packages not provided by Ubuntu
Please use the tool 'ppa-purge' from the ppa-purge 
package to remove software from a Launchpad PPA and 
try the upgrade again.

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 1:18.04.44
ProcVersionSignature: Ubuntu 4.15.0-149.153-generic 4.15.18
Uname: Linux 4.15.0-149-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.24
Architecture: amd64
CrashDB: ubuntu
Date: Thu Jul  1 16:27:44 2021
InstallationDate: Installed on 2019-06-27 (734 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_IN
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2021-07-01 (0 days ago)
VarLogDistupgradeTermlog:
 
mtime.conffile..etc.update-manager.release-upgrades: 2021-03-30T08:40:06.677120

** Affects: ubuntu-release-upgrader (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug bionic dist-upgrade

** Attachment added: "main.log"
   https://bugs.launchpad.net/bugs/1934297/+attachment/5508442/+files/main.log

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https://bugs.launchpad.net/bugs/1934297

Title:
  upgrade to 20.04 from 18.04 unsuccessful

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

Bug description:
  (1)Description:	Ubuntu 18.04.5 LTS
  Release:	18.04

  (2)gnome:
    Installed: (none)
    Candidate: 1:3.22+9
    Version table:
       1:3.22+9 500
          500 http://archive.ubuntu.com/ubuntu bionic/universe amd64 Packages

  (3) I expected the upgrade to 20.04 from 18.04 to happen without any issues.
  (4) The upgrade failed with this error message. I have also attached the contents of /var/log/dist-upgrade/apt.log and /var/log/dist-upgrade/main.log 

  
  An unresolvable problem occurred while calculating the upgrade.

   This was likely caused by:
   * Unofficial software packages not provided by Ubuntu
  Please use the tool 'ppa-purge' from the ppa-purge 
  package to remove software from a Launchpad PPA and 
  try the upgrade again.

  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 1:18.04.44
  ProcVersionSignature: Ubuntu 4.15.0-149.153-generic 4.15.18
  Uname: Linux 4.15.0-149-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.24
  Architecture: amd64
  CrashDB: ubuntu
  Date: Thu Jul  1 16:27:44 2021
  InstallationDate: Installed on 2019-06-27 (734 days ago)
  InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
  PackageArchitecture: all
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_IN
   SHELL=/bin/bash
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to bionic on 2021-07-01 (0 days ago)
  VarLogDistupgradeTermlog:
   
  mtime.conffile..etc.update-manager.release-upgrades: 2021-03-30T08:40:06.677120

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