Handle invalid ranges correctly

This fixes #114

2 files changed, 8 insertions, 1 deletions

diff --git a/src/croniter/croniter.py b/src/croniter/croniter.py
index 3398227..f21e368 100644
--- a/src/croniter/croniter.py
+++ b/src/croniter/croniter.py
@@ -511,7 +511,11 @@ class croniter(object):
                             "[{0}] is not acceptable".format(expr_format))
 
                     low, high, step = map(int, [low, high, step])
-                    rng = range(low, high + 1, step)
+                    try:
+                        rng = range(low, high + 1, step)
+                    except ValueError as exc:
+                        raise CroniterBadCronError(
+                            'invalid range: {0}'.format(exc))
                     e_list += (["{0}#{1}".format(item, nth) for item in rng]
                         if i == 4 and nth else rng)
                 else:
diff --git a/src/croniter/tests/test_croniter.py b/src/croniter/tests/test_croniter.py
index 2d23525..8b30fef 100755
--- a/src/croniter/tests/test_croniter.py
+++ b/src/croniter/tests/test_croniter.py
@@ -832,6 +832,9 @@ class CroniterTest(base.TestCase):
         ts = "{0}".format(datetime.utcfromtimestamp(c.get_prev()))
         self.assertEqual(ts, '2018-01-01 10:00:00')
 
+    def test_invalid_zerorepeat(self):
+        self.assertFalse(croniter.is_valid('*/0 * * * *'))
+
 
 if __name__ == '__main__':
     unittest.main()