'When `byhour` is specified with `freq=HOURLY`, there are certain
combinations of `dtstart` and `byhour` which result in an rrule with no
valid values.
See https://github.com/dateutil/dateutil/issues/4'

def testHourlyBadRRule(self):

    self.assertRaises(ValueError, rrule, HOURLY, **dict(interval=4, byhour=(7, 11, 15, 19), dtstart=datetime(1997, 9, 2, 9, 0)))
