Unresolvable problem with upgrading from 15.04 to 15.10

[Edmond Rosen]

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

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: ubuntu-release-upgrader-core 1:15.04.14.3
ProcVersionSignature: Ubuntu 3.19.0-51.57-generic 3.19.8-ckt13
Uname: Linux 3.19.0-51-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.8
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Mon Feb 22 23:04:39 2016
InstallationDate: Installed on 2013-12-28 (787 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to vivid on 2016-02-23 (0 days ago)
VarLogDistupgradeTermlog: