Incorrect psycopg2.tz.FixedOffsetTimezone after pickling datetimes with different timezones

Submitted by: Robert Saint

>>> before_pickling = []
>>> cur.execute("SET TIME ZONE 'Europe/Rome';")  # UTC + 1 hour
>>> cur.execute("SELECT '2010-01-01 10:30:45'::timestamptz;")
>>> before_pickling.append(cur.fetchone()[0])
>>> cur.execute("SET TIME ZONE 'Europe/Moscow';")  # UTC + 3 hour
>>> cur.execute("SELECT '2010-01-01 10:30:45'::timestamptz;")
>>> before_pickling.append(cur.fetchone()[0])
>>> print before_pickling
[datetime.datetime(2010, 1, 1, 10, 30, 45, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=60, name=None)), 
    datetime.datetime(2010, 1, 1, 10, 30, 45, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None))]
>>> after_pickling = pickle.loads(pickle.dumps(before_pickling))
>>> print before_pickling == after_pickling
False
>>> print after_pickling
[datetime.datetime(2010, 1, 1, 10, 30, 45, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 
    datetime.datetime(2010, 1, 1, 10, 30, 45, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None))]