Make sure locale is what we want before/after the tests

The locale is a global state, and it was not properly reset to
whatever it was before the unitttest possibly changed it.
This is now fixed.

Not restoring the locale led to weird issues: depending on
the order chosen by "python -m unittest discover" to run
the unit tests, some tests would apparently randomly fail
due to the locale not being what was expected.

For example, test_period_in_timeperiod_archive would
call mock('posts/1970/ 1月/index.html',...) instead of
expected mock('posts/1970/Jan/index.html',...) and fail.

pelican/tests/test_utils.py

@@ -354,9 +354,12 @@ class TestCopy(unittest.TestCase):
 
     def setUp(self):
         self.root_dir = mkdtemp(prefix='pelicantests.')
+        self.old_locale = locale.setlocale(locale.LC_ALL)
+        locale.setlocale(locale.LC_ALL, str('C'))
 
     def tearDown(self):
         shutil.rmtree(self.root_dir)
+        locale.setlocale(locale.LC_ALL, self.old_locale)
 
     def _create_file(self, *path):
         with open(os.path.join(self.root_dir, *path), 'w') as f: