[Bug 1852451] Re: upgrade from 16.04 to 18.04 failed

[Ubuntu Foundations Team Bug Bot]

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

** Tags added: xenial2bionic

** This bug has been marked a duplicate of bug 1611737
   Can't upgrade from a release if ros packages are  installed from ROS servers

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https://bugs.launchpad.net/bugs/1852451

Title:
  upgrade from 16.04 to 18.04 failed

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

Bug description:
  Ran into an error while trying to upgrade from Ubuntu 16.04 to 18.04:

  "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."

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: ubuntu-release-upgrader-core 1:16.04.27
  ProcVersionSignature: Ubuntu 4.4.0-168.197-generic 4.4.197
  Uname: Linux 4.4.0-168-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.21
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: Unity
  Date: Wed Nov 13 16:27:13 2019
  InstallationDate: Installed on 2016-06-13 (1248 days ago)
  InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to xenial on 2019-11-13 (0 days ago)
  VarLogDistupgradeTermlog:

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