add test for override

test/test_utils.py

@@ -771,6 +771,8 @@ class TestUtil(unittest.TestCase):
         self.assertEqual(parse_iso8601('2014-03-23T23:04:26+0100'), 1395612266)
         self.assertEqual(parse_iso8601('2014-03-23T23:04:26-07:00'), 1395641066)
         self.assertEqual(parse_iso8601('2014-03-23T23:04:26', timezone=dt.timedelta(hours=-7)), 1395641066)
+        # default does not override timezone in date_str
+        self.assertEqual(parse_iso8601('2014-03-23T23:04:26-07:00',  timezone=dt.timedelta(hours=-10)), 1395641066)
         self.assertEqual(parse_iso8601('2014-03-23T22:04:26+0000'), 1395612266)
         self.assertEqual(parse_iso8601('2014-03-23T22:04:26Z'), 1395612266)
         self.assertEqual(parse_iso8601('2014-03-23T22:04:26.1234Z'), 1395612266)