purge extension doesn't need "#!/usr/bin/env python".
(from the Debian package: deb_specific__hgpurge.py.patch)
--- a/contrib/purge/purge.py
+++ b/contrib/purge/purge.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-#
# Copyright (C) 2006 - Marco Barisione <marco@barisione.org>
#
# This is a small extension for Mercurial (http://www.selenic.com/mercurial)