Upgrade to Ubuntu 14

[Thomas de Vries]

I try to use the automatic update from Ubuntu 13 to 14. I get the following error message:
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.

As suggested, I used the command line to report the bug.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: ubuntu-release-upgrader-core 1:0.205.6
ProcVersionSignature: hostname 3.11.0-26.45-generic 3.11.10.12
Uname: Linux 3.11.0-26-generic i686
ApportVersion: 2.12.5-0ubuntu2.2
Architecture: i386
CrashDB: ubuntu
Date: Sun Jul 27 15:25:32 2014
InstallationDate: Installed on 2014-04-10 (108 days ago)
InstallationMedia: It
MarkForUpload: True
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to saucy on 2014-07-27 (0 days ago)
VarLogDistupgradeTermlog: