upgrade from 12.04 to 14.04.1 failed in setting new software channels

[Simon Tygesen]

when running the recommended upgrade from 12.04 to 14.04 through the update manager the upgrade failed at "setting new software channels".
Possible problems from pkgProblemResolver was that it may be caused by held packages.
Unofficial packages not provided by Ubuntu was removed and upgrade retried, but with same results.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.156.14.17
ProcVersionSignature: Ubuntu 3.13.0-43.72~precise1-generic 3.13.11.11
Uname: Linux 3.13.0-43-generic x86_64
ApportVersion: 2.0.1-0ubuntu17.8
Architecture: amd64
Date: Wed Dec 24 15:03:05 2014
GsettingsChanges:
 com.ubuntu.update-manager first-run false
 com.ubuntu.update-manager launch-time 1419462116
 com.ubuntu.update-manager show-details true
 com.ubuntu.update-manager window-height 1000
 com.ubuntu.update-manager window-width 1215
InstallationMedia: Ubuntu 12.04.3 LTS "Precise Pangolin" - Release amd64 (20130820.1)
MarkForUpload: True
PackageArchitecture: all
SourcePackage: update-manager
Symptom: ubuntu-release-upgrader-core
UpgradeStatus: Upgraded to precise on 2014-12-24 (0 days ago)
VarLogDistupgradeTermlog: