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

I have no idea what happened. The installer (Update Manager) was running in the background and I was initiating a search in the File Manager window when the error message popped up.

ProblemType: Package
DistroRelease: Ubuntu 12.04
Package: sessioninstaller 0.20+bzr128-0ubuntu1.1
ProcVersionSignature: Ubuntu 3.2.0-34.53-generic 3.2.33
Uname: Linux 3.2.0-34-generic i686
ApportVersion: 2.0.1-0ubuntu15
Architecture: i386
Date: Mon Dec 17 18:22:09 2012
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: symbolic link '/usr/lib/python2.7/dist-packages/sessioninstaller/backends/__init__.py' size has changed from 67 to 2
UpgradeStatus: Upgraded to precise on 2012-04-19 (243 days ago)