Delete python bytecode before every test run.

This should eliminate the need to clean -x -i to kill pyc files in
your local directory to get tests to pass.

Change-Id: Icb958a994f0864f11b4f4d091826f3530875fe44
Closes-Bug: #1368661

tox.ini

@@ -19,7 +19,10 @@ setenv =
 deps =
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/test-requirements.txt
-commands = nosetests mistralclient/tests/unit
+commands = 
+    find . -type f -name "*.pyc" -delete
+    nosetests mistralclient/tests/unit
+whitelist_externals = find
 
 [testenv:functional]
 setenv =