Ubuntu distribution upgrade tool displays an error message saying "the upgrade couldn't be configured" while upgrading Ubuntu from Natty to Oneiric.
What happened exactly:
1. Ran update-manager (from gnome GUI).
2. The update manager's window showed up. There was a button for upgrading to Ubuntu 11.10; I clicked it.
3. A confirmation/release notes window appeared. I clicked the 'Upgrade' button again.
4. The upgrade progress window appeared. When the second step (configuring new software channels) began, an info message appeared which said that third-party sources in my "sources.list" were restricted by the update manager.
5. While calculating the changes (still at the second step), the error message appeared. I clicked the 'Close' button. The upgrade stopped and the upgrade tool began rolling back to the installed release (previous state of the system).
Error message text (partial):
An unresolvable problem occurred while calculating the upgrade:
E:Error, pkgProblemResolver::Resolve [...]
ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: update-manager 1:0.150.5.4
ProcVersionSignature: Ubuntu 2.6.38-15.66-generic-pae 2.6.38.8
Uname: Linux 2.6.38-15-generic-pae i686
Architecture: i386
Date: Mon Sep 10 02:26:11 2012
GConfNonDefault:
/apps/update-manager/check_new_release_ignore=
/apps/update-manager/first_run=false
/apps/update-manager/window_size=(600,600)
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
PackageArchitecture: all
ProcEnviron:
LANGUAGE=bg_BG:en
PATH=(custom, user)
LANG=bg_BG.UTF-8
SHELL=/bin/bash
SourcePackage: update-manager
UpgradeStatus: Upgraded to natty on 2012-09-09 (0 days ago)
VarLogDistupgradeApttermlog:
VarLogDistupgradeHistorylog:
VarLogDistupgradeTermlog:
There is a 'term.log' file in /var/log/