clone_member.py must be a symbolic link pointing to the clone_member
script in the Mailman bin directory; you could create this with
something like the following:

ln -s /usr/lib/mailman/bin/clone_member clone_member.py

This isn't something that can be skipped, mailman_admin_cmd_handler.py
*requires* symlinks for both clone_member.py and list_members.py to
their script counterparts in the Mailman bin directory.