delete python bytecode including pyo before every test run

Change-Id: I435274c0010ceb7595b2e8c83848b010a9b42edd

tox.ini

@@ -9,7 +9,7 @@ usedevelop = True
 install_command = pip install -U {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = find . -type f -name "*.pyc" -delete
+commands = find . -type f -name "*.py[c|o]" -delete
            python setup.py testr --slowest --testr-args='{posargs}'
 whitelist_externals = find