[Bug 1622329] [NEW] Ubuntu 14.04.5 LTS upgrade to 16 fails via Software Updater

[Artem V L]

Public bug reported:

On the attempt to upgrade Ubuntu 14 to 16 via the Software Updater the
following dialog window appears:

Could not calculate the upgrade

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

If none of this applies, then please report this bug using the command
'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.


This dialog appears on the second step of the upgrade:
Preparing to upgrade  [OK]
Setting new software channels  <- Fails
...

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.8
ProcVersionSignature: Ubuntu 3.13.0-95.142-generic 3.13.11-ckt39
Uname: Linux 3.13.0-95-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.21
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Sun Sep 11 13:57:14 2016
EcryptfsInUse: Yes
InstallationDate: Installed on 2014-10-25 (686 days ago)
InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2016-09-11 (0 days ago)
VarLogDistupgradeTermlog:

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


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

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https://bugs.launchpad.net/bugs/1622329

Title:
  Ubuntu 14.04.5 LTS upgrade to 16 fails via Software Updater

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

Bug description:
  On the attempt to upgrade Ubuntu 14 to 16 via the Software Updater the
  following dialog window appears:

  Could not calculate the upgrade

  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

  If none of this applies, then please report this bug using the command
  'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.

  
  This dialog appears on the second step of the upgrade:
  Preparing to upgrade  [OK]
  Setting new software channels  <- Fails
  ...

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: ubuntu-release-upgrader-core 1:0.220.8
  ProcVersionSignature: Ubuntu 3.13.0-95.142-generic 3.13.11-ckt39
  Uname: Linux 3.13.0-95-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.21
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: Unity
  Date: Sun Sep 11 13:57:14 2016
  EcryptfsInUse: Yes
  InstallationDate: Installed on 2014-10-25 (686 days ago)
  InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to trusty on 2016-09-11 (0 days ago)
  VarLogDistupgradeTermlog:

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