Message "Can't install 'ubuntu-desktop'" during upgrade 14.10>15.04

[Torben Gundtofte-Bruun]

OS version = Ubuntu 14.10
package version = unsure, but it's the automatic Ubuntu updater in Ubuntu 14.10.
Expected = no error.
Actual = Ubuntu notified me that there's a new version available. I confirmed that I wanted to upgrade, and the window "Distribution Upgrade" started working:

quote:
Upgrading Ubuntu to version 15.04
v Preparing to upgrade
> Setting new software channels
unquote.

At this stage, an error was displayed:

quote:
Can't install 'ubuntu-desktop'

It was impossible to install a required package. Please report this as a bug using 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.

[OK]
unquote.

After clicking "OK" the installer seems to have continued okay anyway.

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: ubuntu-release-upgrader-core 1:14.10.10
ProcVersionSignature: Ubuntu 3.16.0-37.51-generic 3.16.7-ckt9
Uname: Linux 3.16.0-37-generic x86_64
ApportVersion: 2.14.7-0ubuntu8.4
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Fri May 8 19:16:31 2015
InstallationDate: Installed on 2013-08-27 (618 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to utopic on 2015-05-08 (0 days ago)
VarLogDistupgradeTermlog:

[Ubuntu Foundations Team Bug Bot (crichton)]

Reviewing the files from your upgrade attempt you seem to have enabled the xorg-edgers-ppa. This will prevent the upgrade as that PPA contains different versions of packages essential to Ubuntu. The page, https://launchpad.net/~xorg-edgers/+archive/ppa, contains details on to how to revert to the official Xorg packages. Thanks.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug 1069133, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.
[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]