              'username': 'foo',
              'usersite_set-TOTAL_FORMS': '1',
              'usersite_set-INITIAL_FORMS': '1',
              'usersite_set-MAX_NUM_FORMS': '1',
              'usersite_set-0-id': six.text_type(us.pk),
              'usersite_set-0-data': '7',
              'usersite_set-0-user': 'foo',
              'usersite_set-0-DELETE': '1'
          }
          formset = formset_cls(data, instance=u)
 
</s>
            'usersite_set-0-id': str(us.pk),
              'username': 'foo',
              'usersite_set-TOTAL_FORMS': '1',
              'usersite_set-INITIAL_FORMS': '1',
              'usersite_set-MAX_NUM_FORMS': '1',
            'usersite_set-0-id': str(us.pk),
              'usersite_set-0-data': '7',
              'usersite_set-0-user': 'foo',
              'usersite_set-0-DELETE': '1'
          }
          formset = formset_cls(data, instance=u)
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_regress/tests.py