Delete python bytecode before every test run

Bring over the cleaning line from run_tests.sh for the pyc files to
all the tox runs.

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

Change-Id: I3e1c53a26440aaff5dd92cd5381d71a1d411ebe8
Closes-Bug: #1368661

tox.ini

@@ -6,10 +6,13 @@ skipsdist = True
 setenv = VIRTUAL_ENV={envdir}
 usedevelop = True
 install_command = pip install -U {opts} {packages} --pre
+whitelist_externals = find
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
        MySQL-python
-commands = nosetests
+commands =
+ find . -type f -name "*.pyc" -delete
+ nosetests
 
 [testenv:py27-postgres]
 deps = -r{toxinidir}/requirements.txt