'Ensure required cant be None / Empty.'

def test_complex_field_required(self):

    class Simple(Document, ):
        mapping = ListField(required=True)
    Simple.drop_collection()
    e = Simple()
    e.mapping = []
    self.assertRaises(ValidationError, e.save)
    class Simple(Document, ):
        mapping = DictField(required=True)
    Simple.drop_collection()
    e = Simple()
    e.mapping = {}
    self.assertRaises(ValidationError, e.save)
