clear pycache and remove all pyc/pyo before starting unit test

Delete python bytecode before every test run.
Because python creates pyc files during tox runs, certain
changes in the tree, like deletes of files, or switching
branches, can create spurious errors.

Closes-Bug: #1368661
Change-Id: Iedcb400fa3b0417f5bb8e943b17758fcfb4070c6

test/unit/common/middleware/test_xprofile.py

@@ -458,17 +458,17 @@ class Test_html_viewer(unittest.TestCase):
                               self.log_files)
 
     def test_format_source_code(self):
-        nfl_os = '%s:%d(%s)' % (os.__file__[:-1], 136, 'makedirs')
-        self.assertTrue('makedirs' in self.viewer.format_source_code(nfl_os))
-        self.assertFalse('makedirsXYZ' in
-                         self.viewer.format_source_code(nfl_os))
-        nfl_illegal = '%s:136(makedirs)' % os.__file__
-        self.assertTrue(_('The file type are forbidden to access!') in
-                        self.viewer.format_source_code(nfl_illegal))
-        nfl_not_exist = '%s.py:136(makedirs)' % os.__file__
-        expected_msg = _('Can not access the file %s.') % os.__file__
-        self.assertTrue(expected_msg in
-                        self.viewer.format_source_code(nfl_not_exist))
+        osfile = os.__file__.rstrip('c')
+        nfl_os = '%s:%d(%s)' % (osfile, 136, 'makedirs')
+        self.assertIn('makedirs', self.viewer.format_source_code(nfl_os))
+        self.assertNotIn('makedirsXYZ', self.viewer.format_source_code(nfl_os))
+        nfl_illegal = '%sc:136(makedirs)' % osfile
+        self.assertIn(_('The file type are forbidden to access!'),
+                      self.viewer.format_source_code(nfl_illegal))
+        nfl_not_exist = '%s.py:136(makedirs)' % osfile
+        expected_msg = _('Can not access the file %s.py.') % osfile
+        self.assertIn(expected_msg,
+                      self.viewer.format_source_code(nfl_not_exist))
 
 
 class TestStats2(unittest.TestCase):

tox.ini

@@ -12,7 +12,10 @@ setenv = VIRTUAL_ENV={envdir}
 deps =
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
-commands = nosetests {posargs:test/unit}
+commands = find . -type f -name "*.py[c|o]" -delete
+           find . -type d -name "__pycache__" -delete
+           nosetests {posargs:test/unit}
+whitelist_externals = find
 passenv = SWIFT_* *_proxy
 
 [testenv:cover]