Add support for stdlib datetime.timezone instances (#93)

* Add support for stdlib datetime.timezone instances

* Turns out that test is only safe to run on >= 3.2

* Update PR after @sdispater feedback

- Fixed a total_seconds() misuse
- Simplified our fallback logic to always use utcoffset() when we have a
  tzinfo instance that isn't pytz
- Added an additional assertion to our test, ensuring non-UTC
  `datetime.timezone` instances can be set

* Remove unnecessary try/catch

Author: klardotsh

pendulum/pendulum.py

@@ -70,16 +70,11 @@ def _safe_create_datetime_zone(cls, obj):
         elif isinstance(obj, datetime.tzinfo) and not isinstance(obj, Timezone):
             # pytz
             if hasattr(obj, 'localize'):
-                obj = obj.zone
-            else:
-                # We have no sure way to figure out
-                # the timezone name, we raise an error
-
-                raise ValueError('Unsupported timezone {}'.format(obj))
+                return cls._timezone(obj.zone)
 
-        tz = cls._timezone(obj)
+            return FixedTimezone(obj.utcoffset(None).total_seconds())
 
-        return tz
+        return cls._timezone(obj)
 
     @classmethod
     def _local_timezone(cls):

tests/pendulum_tests/test_timezone.py

@@ -1,9 +1,13 @@
 # -*- coding: utf-8 -*-
 
+import sys
 from pendulum import Pendulum
 
 from .. import AbstractTestCase
 
+if sys.version_info >= (3, 2):
+    from datetime import timedelta, timezone
+
 
 class TimezoneTest(AbstractTestCase):
 
@@ -36,3 +40,12 @@ def test_astimezone(self):
         d = d.astimezone('Europe/Paris')
         self.assertEqual('Europe/Paris', d.timezone_name)
         self.assertPendulum(d, now.year, now.month, now.day, now.hour + 1, now.minute)
+
+        if sys.version_info >= (3, 2):
+            d = d.astimezone(timezone.utc)
+            self.assertEqual('+00:00', d.timezone_name)
+            self.assertPendulum(d, now.year, now.month, now.day, now.hour, now.minute)
+
+            d = d.astimezone(timezone(timedelta(hours=-8)))
+            self.assertEqual('-08:00', d.timezone_name)
+            self.assertPendulum(d, now.year, now.month, now.day, now.hour - 8, now.minute)