postrm is in maas-common 1.2+bzr1373+dfsg-0ubuntu1~12.04.6.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 | #!/bin/sh
set -e
case "$1" in
        purge)
                # Deleting user/group
                if getent passwd maas >/dev/null; then
                        deluser maas || true
                        delgroup maas || true
                fi
esac
 |