Comment 3 for bug 946454

(copying verbatim from my forum comment)
You're in luck. By happy coincidence we're also mailman users so I experienced this issue myself when I was tested the latest version of turnkey-pylib.

Long story short, edit /etc/mailman/postfix-to-mailman.py and change the line after import sys.os like this:

import sys, os
sys.path.insert(0, "/usr/lib/mailman/bin")
import paths

What's going on? Mailman broke due to a freakish interaction with turnkey-pylib.

turnkey-pylib has a paths.py module. So does mailman. Normally this wouldn't be a problem as local modules are preferred over system modules. But the postfix-to-mailman.py script is installed in /etc/mailman so /usr/lib/mailman/bin/paths.py isn't even in its path.

The postfix-to-mailman.py attempts to correct this by manipulating sys.path but it does so incorrectly by appending /usr/lib/mailman/bin to sys.path instead of inserting it at the beginning.

That's why turnkey-pylib's paths.py overrode mailman's paths.py.