A quick search on Google came up with something that I knew someone must have written: pycmail, A Procmail Replacement in Python.
Everytime I tinker with my procmail scripts I have the feel that I might touch a live wire and get electrocuted. The syntax is so terse and easy to forget that you are bound to make a mistake. Turning on the full logging has helped though. A least you can see it's lizard brain chundering through the script after the fact.
I wonder if pycmail will be any better...