The package 'unity' is marked for removal but it is in the removal blacklist.

Attempted to upgrade from 12.04 to 12.10 and error reported that An unresolvable problem occurred while calculating the upgrade:
The package 'unity' is marked for removal but it is in the removal blacklist.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.156.14.11
ProcVersionSignature: Ubuntu 3.2.0-41.66-generic-pae 3.2.42
Uname: Linux 3.2.0-41-generic-pae i686
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu17.2
Architecture: i386
Date: Tue May 7 18:39:12 2013
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_NZ:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_NZ.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
Symptom: ubuntu-release-upgrader-core
UpgradeStatus: Upgraded to precise on 2013-05-07 (0 days ago)
VarLogDistupgradeAptclonesystemstate.tar.gz: Error: [Errno 13] Permission denied: '/var/log/dist-upgrade/apt-clone_system_state.tar.gz'
VarLogDistupgradeTermlog: