def _add_tzinfo(self, datetime_obj, tz_string):
if datetime_obj is None:<EOL><INDENT>return None<EOL><DEDENT>tzinfo_match = tz.gettz(tz_string)<EOL>return datetime_obj.replace(tzinfo=tzinfo_match)<EOL>
take a naive datetime and add dateutil.tz.tzinfo object

:param datetime_obj: naive datetime object
:return: datetime object with tzinfo