Comment 2 for bug 1075632

It looks to me like there's a common issue with upgrading python packages in some situations - google finds ~230 bugs in launchpad in with the same error message, and the sample I looked at seemed to be in packages which only seemed to be related by being in python:

https://www.google.com/search?q=site%3Abugs.launchpad.net%2Fbugs+%22ErrorMessage%3A+subprocess+installed+post-installation+script+returned+error+exit+status+101%22