'ManyToManyField accepts the ``through_fields`` kwarg
only if an intermediary table is specified.'

def test_m2m_field_argument_validation(self):

    class Fan(models.Model, ):
        pass
    with self.assertRaisesMessage(ValueError, 'Cannot    specify    through_fields    without    a    through    model'):
        models.ManyToManyField(Fan, through_fields=('f1', 'f2'))
