update-manager crash when upgrading from trusty to utopic

[Steve Langasek]

Running 'update-manager -d' on my laptop to upgrade from trusty to utopic, it crashed (after getting rather far along) with the following backtrace:

Traceback (most recent call last):
  File "/tmp/ubuntu-release-upgrader-nthx97q4/utopic", line 8, in <module>
    sys.exit(main())
  File "/tmp/ubuntu-release-upgrader-nthx97q4/DistUpgrade/DistUpgradeMain.py", line 239, in main
    if app.run():
  File "/tmp/ubuntu-release-upgrader-nthx97q4/DistUpgrade/DistUpgradeController.py", line 1820, in run
    return self.fullUpgrade()
  File "/tmp/ubuntu-release-upgrader-nthx97q4/DistUpgrade/DistUpgradeController.py", line 1798, in fullUpgrade
    self.doPostUpgrade()
  File "/tmp/ubuntu-release-upgrader-nthx97q4/DistUpgrade/DistUpgradeController.py", line 1249, in doPostUpgrade
    remove_candidates = now_obsolete - self.obsolete_pkgs
TypeError: unsupported operand type(s) for -: 'set' and 'list'
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 102, in apport_excepthook
    pr.add_proc_info(extraenv=['PYTHONPATH', 'PYTHONHOME'])
  File "/usr/lib/python3/dist-packages/apport/report.py", line 523, in add_proc_info
    raise ValueError('%s does not exist' % self['ExecutablePath'])
ValueError: /usr/bin/python3.4 (deleted) does not exist

Original exception was:
Traceback (most recent call last):
  File "/tmp/ubuntu-release-upgrader-nthx97q4/utopic", line 8, in <module>
    sys.exit(main())
  File "/tmp/ubuntu-release-upgrader-nthx97q4/DistUpgrade/DistUpgradeMain.py", line 239, in main
    if app.run():
  File "/tmp/ubuntu-release-upgrader-nthx97q4/DistUpgrade/DistUpgradeController.py", line 1820, in run
    return self.fullUpgrade()
  File "/tmp/ubuntu-release-upgrader-nthx97q4/DistUpgrade/DistUpgradeController.py", line 1798, in fullUpgrade
    self.doPostUpgrade()
  File "/tmp/ubuntu-release-upgrader-nthx97q4/DistUpgrade/DistUpgradeController.py", line 1249, in doPostUpgrade
    remove_candidates = now_obsolete - self.obsolete_pkgs
TypeError: unsupported operand type(s) for -: 'set' and 'list'

This seems to happen at the end of the upgrade - ''apt-get -f install' / 'apt-get dist-upgrade' shows no packages pending.

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: ubuntu-release-upgrader-core 1:14.10.3
ProcVersionSignature: Ubuntu 3.13.0-24.47-generic 3.13.9
Uname: Linux 3.13.0-24-generic x86_64
ApportVersion: 2.14.2-0ubuntu4
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Thu May 22 22:54:50 2014
InstallationDate: Installed on 2010-09-24 (1336 days ago)
InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to utopic on 2014-05-23 (0 days ago)
VarLogDistupgradeTermlog:

[Colin Law (colin-law)]

Is this a dup of bug #1322363?