cleanup .pyc update hook

[chadrik]

does anyone have an update hook that deletes .pyc's for python files  
that were removed during update?  they stick around even after the  
python files get removed so it can lead to some serious wtf moments.  
in starting to write my hook i got hung up trying to figure out how to  
get a list of the files that were just removed, so before i invest a  
lot of time in this, just wanted to make sure i'm not reinventing the  
wheel.

thanks,
chad