[Bug 1650616] [NEW] cannot upgrade to 16.04

[Nisho Matsushita]

Public bug reported:

When I run `do-release-upgrade` on terminal in order to upgrade to 16.04, it says 
"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".
But I have no idea what caused this error.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.9
ProcVersionSignature: Ubuntu 3.13.0-106.153-generic 3.13.11-ckt39
Uname: Linux 3.13.0-106-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.23
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Sat Dec 17 01:21:26 2016
InstallationDate: Installed on 2014-03-01 (1021 days ago)
InstallationMedia: Ubuntu 12.04.3 LTS "Precise Pangolin" - Release amd64 (20130820.1)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2016-12-16 (0 days ago)
mtime.conffile..etc.update.manager.release.upgrades: 2016-08-06T12:33:04.268494

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


** Tags: amd64 apport-bug dist-upgrade trusty

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https://bugs.launchpad.net/bugs/1650616

Title:
  cannot upgrade to 16.04

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

Bug description:
  When I run `do-release-upgrade` on terminal in order to upgrade to 16.04, it says 
  "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".
  But I have no idea what caused this error.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: ubuntu-release-upgrader-core 1:0.220.9
  ProcVersionSignature: Ubuntu 3.13.0-106.153-generic 3.13.11-ckt39
  Uname: Linux 3.13.0-106-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.23
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: Unity
  Date: Sat Dec 17 01:21:26 2016
  InstallationDate: Installed on 2014-03-01 (1021 days ago)
  InstallationMedia: Ubuntu 12.04.3 LTS "Precise Pangolin" - Release amd64 (20130820.1)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to trusty on 2016-12-16 (0 days ago)
  mtime.conffile..etc.update.manager.release.upgrades: 2016-08-06T12:33:04.268494

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