              'form-0-id': six.text_type(poet.id),
              'form-0-name': 'test',
              'form-1-id': '',
              'form-1-name': 'x' * 1000,  # Too long
              'form-2-id': six.text_type(poet.id),  # Violate unique constraint
              'form-2-name': 'test2',
          }
          formset = PoetFormSet(data, queryset=Poet.objects.all())
          # Make sure this form doesn't pass validation.
          self.assertIs(formset.is_valid(), False)
 
</s> remove             'form-0-id': six.text_type(poet.id),
 </s> add             'form-0-id': str(poet.id), </s> remove             'form-0-id': six.text_type(poet.id),
 </s> add             'form-0-id': str(poet.id), </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': 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         if not isinstance(self.file_path, six.string_types):
 </s> add         if not isinstance(self.file_path, str):
            'form-2-id': str(poet.id),  # Violate unique constraint
              'form-0-id': six.text_type(poet.id),
              'form-0-name': 'test',
              'form-1-id': '',
              'form-1-name': 'x' * 1000,  # Too long
            'form-2-id': str(poet.id),  # Violate unique constraint
              'form-2-name': 'test2',
          }
          formset = PoetFormSet(data, queryset=Poet.objects.all())
          # Make sure this form doesn't pass validation.
          self.assertIs(formset.is_valid(), False)
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