osmoappdesc.py, tests: switch to python 3

Make build and external tests work with python3, so we can drop
the python2 dependency.

This should be merged shortly after osmo-python-tests was migrated to
python3, and the jenkins build slaves were (automatically) updated to
have the new osmo-python-tests installed.

Related: OS#2819
Depends: osmo-python-tests I3ffc3519bf6c22536a49dad7a966188ddad351a7
Change-Id: I53ccde96dd3785098df0f7d693c504c8b8302e90
diff --git a/osmoappdesc.py b/osmoappdesc.py
index bd7fea3..b7a274c 100644
--- a/osmoappdesc.py
+++ b/osmoappdesc.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # (C) 2013 by Katerina Barone-Adesi <kat.obsc@gmail.com>
 # This program is free software: you can redistribute it and/or modify