package sessioninstaller 0.20+bzr128-0ubuntu1.1 failed to install/upgrade: ErrorMessage: symbolic link '/usr/lib/python2.7/dist-packages/sessioninstaller/backends/__init__.py' size has changed from 67 to 2

Attempting to install Ubuntu Web Apps (more accurately, the upgrade part of the process), Update Manager attempted a "partial ugrade" and this error, among others, occured.

ProblemType: Package
DistroRelease: Ubuntu 12.04
Package: sessioninstaller 0.20+bzr128-0ubuntu1.1
ProcVersionSignature: Ubuntu 3.2.0-45.70-generic 3.2.44
Uname: Linux 3.2.0-45-generic i686
ApportVersion: 2.0.1-0ubuntu17.3
Architecture: i386
Date: Wed Jun 12 16:45:05 2013
ErrorMessage: ErrorMessage: symbolic link '/usr/lib/python2.7/dist-packages/sessioninstaller/backends/__init__.py' size has changed from 67 to 2
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
MarkForUpload: True
PackageArchitecture: all
SourcePackage: sessioninstaller
Title: package sessioninstaller 0.20+bzr128-0ubuntu1.1 failed to install/upgrade: ErrorMessage: symbolic link '/usr/lib/python2.7/dist-packages/sessioninstaller/backends/__init__.py' size has changed from 67 to 2
UpgradeStatus: Upgraded to precise on 2013-06-12 (0 days ago)