[Bug 1890989] Re: can't upgrade to ubuntu 20.04.1 LTS , says caused by unofficial software packages not provided by ubuntu

[Chris Guiver]

Thank you for taking the time to report this issue and helping to make
Ubuntu better.

I see numerous 'ros-melodic*' packages which are 3rd party (from PPA or other 3rd party source) as not found on https://packages.ubuntu.com/search?suite=all&arch=any&searchon=names&keywords=ros-melodic or Ubuntu repositories for any release.
https://help.ubuntu.com/community/Repositories/Ubuntu

If you need support on the use of ppa-purge, this bug report can be
converted to a question, or you can ask a question at
https://answers.launchpad.net/ubuntu. You can also find help with your
problem in the support forum of your local Ubuntu community
http://loco.ubuntu.com/ or asking at https://askubuntu.com or
https://ubuntuforums.org, or for more support options please look at
https://discourse.ubuntu.com/t/community-support/709

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https://bugs.launchpad.net/bugs/1890989

Title:
  can't upgrade to ubuntu 20.04.1 LTS , says caused by unofficial
  software packages not provided by ubuntu

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

Bug description:
  ubuntu release: 
  Description:	Ubuntu 18.04.5 LTS
  Release:	18.04



  
  Error output: 

  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'. 

  
  Restoring original system state

  Aborting
  Reading package lists... Done    
  Building dependency tree          
  Reading state information... Done

  main.log :

  2020-08-10 11:44:24,081 ERROR Dist-upgrade failed: 'E:Error,
  pkgProblemResolversolver::Resolve generated breaks, this may be caused
  by held packages.'

  2020-08-10 11:44:24,082 DEBUG abort called

  purged all rc status files but still unresolved

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: ubuntu-release-upgrader-core 1:18.04.38
  ProcVersionSignature: Ubuntu 5.4.0-42.46~18.04.1-generic 5.4.44
  Uname: Linux 5.4.0-42-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.16
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: ubuntu:GNOME
  Date: Mon Aug 10 11:49:54 2020
  InstallationDate: Installed on 2020-01-04 (219 days ago)
  InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to bionic on 2020-08-10 (0 days ago)
  mtime.conffile..etc.update-manager.release-upgrades: 2020-08-10T11:20:53.956256

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