tests: Stop requiring python2 for module tests

And make the modules executable, so we can run them in unit tests.

Part of 30063.

lib/chutney/Debug.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 #
 # Copyright 2011 Nick Mathewson, Michael Stone
 # Copyright 2013 The Tor Project

lib/chutney/Templating.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 #
 # Copyright 2011 Nick Mathewson, Michael Stone
 #

lib/chutney/TorNet.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 #
 # Copyright 2011 Nick Mathewson, Michael Stone
 # Copyright 2013 The Tor Project

lib/chutney/Traffic.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 #
 # Copyright 2013 The Tor Project
 #