'get_choices() works with Iterators.'

def test_iterator_choices(self):

    self.assertEqual(WhizIter(c=1).c, 1)
    self.assertEqual(WhizIter(c=9).c, 9)
    self.assertIsNone(WhizIter(c=None).c)
    self.assertEqual(WhizIter(c='').c, '')
