          data = {
              'membership_set-TOTAL_FORMS': '1',
              'membership_set-INITIAL_FORMS': '0',
              'membership_set-MAX_NUM_FORMS': '',
              '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')),
              'membership_set-0-karma': '',
          }
          formset = FormSet(data, instance=person)
          self.assertTrue(formset.is_valid())
  
 
</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             '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             'ownerprofile-0-owner': six.text_type(owner1.auto_id),
 </s> add             'ownerprofile-0-owner': str(owner1.auto_id), </s> remove             'manager_set-0-id': six.text_type(manager[0]['id']),
 </s> add             'manager_set-0-id': str(manager[0]['id']), </s> remove             'usersite_set-0-id': six.text_type(usersite[0]['id']),
 </s> add             'usersite_set-0-id': str(usersite[0]['id']),
            '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'),
          data = {
              'membership_set-TOTAL_FORMS': '1',
              'membership_set-INITIAL_FORMS': '0',
              'membership_set-MAX_NUM_FORMS': '',
            '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'),
            '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'),
              'membership_set-0-karma': '',
          }
          formset = FormSet(data, instance=person)
          self.assertTrue(formset.is_valid())
  
keep keep keep keep replace 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