          data = {
              'owner_set-TOTAL_FORMS': '3',
              'owner_set-INITIAL_FORMS': '1',
              'owner_set-MAX_NUM_FORMS': '',
              'owner_set-0-auto_id': six.text_type(owner1.auto_id),
              'owner_set-0-name': 'Joe Perry',
              'owner_set-1-auto_id': '',
              'owner_set-1-name': 'Jack Berry',
              'owner_set-2-auto_id': '',
              'owner_set-2-name': '',
 
</s> remove             'membership_set-0-date_joined': six.text_type(now.strftime('%Y-%m-%d %H:%M:%S')),
            'initial-membership_set-0-date_joined': six.text_type(now.strftime('%Y-%m-%d %H:%M:%S')),
 </s> add             'membership_set-0-date_joined': now.strftime('%Y-%m-%d %H:%M:%S'),
            'initial-membership_set-0-date_joined': now.strftime('%Y-%m-%d %H:%M:%S'), </s> remove             'membership_set-0-date_joined_0': six.text_type(now.strftime('%Y-%m-%d')),
            'membership_set-0-date_joined_1': six.text_type(now.strftime('%H:%M:%S')),
            'initial-membership_set-0-date_joined': six.text_type(now.strftime('%Y-%m-%d %H:%M:%S')),
 </s> add             'membership_set-0-date_joined_0': now.strftime('%Y-%m-%d'),
            'membership_set-0-date_joined_1': now.strftime('%H:%M:%S'),
            'initial-membership_set-0-date_joined': now.strftime('%Y-%m-%d %H:%M:%S'), </s> remove             'membership_set-0-date_joined': six.text_type(one_day_later.strftime('%Y-%m-%d %H:%M:%S')),
            'initial-membership_set-0-date_joined': six.text_type(now.strftime('%Y-%m-%d %H:%M:%S')),
 </s> add             'membership_set-0-date_joined': one_day_later.strftime('%Y-%m-%d %H:%M:%S'),
            'initial-membership_set-0-date_joined': now.strftime('%Y-%m-%d %H:%M:%S'), </s> remove             'form-0-id': six.text_type(poet.id),
 </s> add             'form-0-id': str(poet.id), </s> remove         lazy_func = lazy(lambda: '', six.text_type)
        self.assertIsInstance(CharField().get_prep_value(lazy_func()), six.text_type)
 </s> add         lazy_func = lazy(lambda: '', str)
        self.assertIsInstance(CharField().get_prep_value(lazy_func()), str)
            'owner_set-0-auto_id': str(owner1.auto_id),
          data = {
              'owner_set-TOTAL_FORMS': '3',
              'owner_set-INITIAL_FORMS': '1',
              'owner_set-MAX_NUM_FORMS': '',
            'owner_set-0-auto_id': str(owner1.auto_id),
              'owner_set-0-name': 'Joe Perry',
              'owner_set-1-auto_id': '',
              'owner_set-1-name': 'Jack Berry',
              'owner_set-2-auto_id': '',
              'owner_set-2-name': '',
keep keep keep keep replace keep keep keep keep keep
 Refs #23919 -- Removed six.<various>_types usage

Thanks Tim Graham and Simon Charette for the reviews. 
tests/model_formsets/tests.py