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_settings.py

@@ -16,10 +16,15 @@ class TestSettingsConfiguration(unittest.TestCase):
     optimizations.
     """
     def setUp(self):
+        self.old_locale = locale.setlocale(locale.LC_ALL)
+        locale.setlocale(locale.LC_ALL, str('C'))
         self.PATH = abspath(dirname(__file__))
         default_conf = join(self.PATH, 'default_conf.py')
         self.settings = read_settings(default_conf)
 
+    def tearDown(self):
+        locale.setlocale(locale.LC_ALL, self.old_locale)
+
     def test_overwrite_existing_settings(self):
         self.assertEqual(self.settings.get('SITENAME'), "Alexis' log")
         self.assertEqual(self.settings.get('SITEURL'),