Bug in Mailman version 2.1.10
We're sorry, we hit a bug!
Please inform the webmaster for this site of this problem. Printing of
traceback and other system information has been explicitly inhibited,
but the webmaster can find this information in the Mailman error logs.
This at http://www.archlinux.org/mailman/listinfo/ , thought about
Some one did a pacman -Syu again? :P