get_next("* * 31 2 *") will raise ValueError after a long time.

[binzeehale]

croniter will not raise erorr , but it will be error when i call get_next.
The most important: this crontab string will cause a long loop before the error happened.

[josegonzalez]

Interestingly, on the latest master, this returns an exception about failing to find the previous date...

$ python src/croniter/tests/test_croniter.py
............................E.
======================================================================
ERROR: test_bug34 (__main__.CroniterTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "src/croniter/tests/test_croniter.py", line 394, in test_bug34
    n1 = itr.get_next(datetime)
  File "/Users/jose/Apps/seatgeek/oss/croniter/src/croniter/croniter.py", line 142, in get_next
    return self._get_next(ret_type or self._ret_type, is_prev=False)
  File "/Users/jose/Apps/seatgeek/oss/croniter/src/croniter/croniter.py", line 228, in _get_next
    result = self._calc(self.cur, expanded, is_prev)
  File "/Users/jose/Apps/seatgeek/oss/croniter/src/croniter/croniter.py", line 366, in _calc
    raise Exception("failed to find prev date")
Exception: failed to find prev date

----------------------------------------------------------------------
Ran 30 tests in 0.037s

FAILED (errors=1)