Force usage with python2

grml2usb isn't py3k-ready yet, so until we're there
ensure we don't run under python3, even by accident.

Closes: #921327

grml2usb

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 # -*- coding: utf-8 -*-
 # pylint: disable-msg=C0302
 """