[Bug 1898969] [NEW] updating os from 16.04 to 18.04 fails

[Arun]

*** This bug is a duplicate of bug 1611737 ***
    https://bugs.launchpad.net/bugs/1611737

Public bug reported:

This is the message which pops.

Could not calculate the upgrade

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 16.04
Package: ubuntu-release-upgrader-core 1:16.04.30
ProcVersionSignature: Ubuntu 4.15.0-118.119~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-118-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.25
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Thu Oct  8 09:48:05 2020
InstallationDate: Installed on 2019-11-28 (314 days ago)
InstallationMedia: Ubuntu 16.04.6 LTS "Xenial Xerus" - Release amd64 (20190227)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2020-10-08 (0 days ago)
VarLogDistupgradeTermlog:
 
mtime.conffile..etc.update-manager.release-upgrades: 2020-10-08T09:10:36.554531

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


** Tags: amd64 apport-bug dist-upgrade third-party-packages xenial xenial2bionic

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https://bugs.launchpad.net/bugs/1898969

Title:
  updating os from 16.04 to 18.04 fails

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

Bug description:
  This is the message which pops.

  Could not calculate the upgrade

  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 16.04
  Package: ubuntu-release-upgrader-core 1:16.04.30
  ProcVersionSignature: Ubuntu 4.15.0-118.119~16.04.1-generic 4.15.18
  Uname: Linux 4.15.0-118-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.25
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: Unity
  Date: Thu Oct  8 09:48:05 2020
  InstallationDate: Installed on 2019-11-28 (314 days ago)
  InstallationMedia: Ubuntu 16.04.6 LTS "Xenial Xerus" - Release amd64 (20190227)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to xenial on 2020-10-08 (0 days ago)
  VarLogDistupgradeTermlog:
   
  mtime.conffile..etc.update-manager.release-upgrades: 2020-10-08T09:10:36.554531

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