[Bug 1414987] Re: Upgrading from 12.04.5 LTS to 14.04.1 LTS reports unresolvable issues

[Corben]

Found a solution to my problem.
A package from ppa:irie/blender caused the problems. It installed a python3 version, which couldn't be upgraded. After uninstalling this package, the upgrade went through.

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https://bugs.launchpad.net/bugs/1414987

Title:
  Upgrading from 12.04.5 LTS to 14.04.1 LTS reports unresolvable issues

Status in update-manager package in Ubuntu:
  New

Bug description:
  Tried today to upgrade from 12.04.5 LTS to 14.04.1 LTS.
  First try resulted in errors with ubuntu-desktop package, which wasn't installed. I installed it manually, and now this error message occurs:

  An unresolvable problem occurred while calculating the upgrade.

   This can be caused by:
   * Upgrading to a pre-release version of Ubuntu
   * Running the current pre-release version of Ubuntu
   * Unofficial software packages not provided by Ubuntu

  Cannot upgrade from 12.04 to 14.04 now.

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: update-manager 1:0.156.14.17
  ProcVersionSignature: Ubuntu 3.2.0-75.110-generic 3.2.64
  Uname: Linux 3.2.0-75-generic x86_64
  NonfreeKernelModules: nvidia
  ApportVersion: 2.0.1-0ubuntu17.8
  Architecture: amd64
  Date: Tue Jan 27 11:42:43 2015
  InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
  MarkForUpload: True
  PackageArchitecture: all
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   LANG=de_DE.UTF-8
   SHELL=/bin/bash
  SourcePackage: update-manager
  Symptom: ubuntu-release-upgrader-core
  UpgradeStatus: Upgraded to precise on 2015-01-27 (0 days ago)

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