Update sudoers.sh

"Sorry, user vagrant is not allowed to execute '/bin/sh -c echo SUDO-SUCCESS-sbawtdhzwzxpqlbsucskxmklqogloqyu; /usr/bin/python /tmp/ansible-tmp-1396539205.79-85165511766742/postgresql_user' as postgres on vagrant.vm."
I also encountered the same problem. 
It should be corrected.
See also mitchellh/vagrant#892