                  model = Document
                  fields = '__all__'
  
          form = DocumentForm()
          self.assertIn('name="myfile"', six.text_type(form))
          self.assertNotIn('myfile-clear', six.text_type(form))
          form = DocumentForm(files={'myfile': SimpleUploadedFile('something.txt', b'content')})
          self.assertTrue(form.is_valid())
          doc = form.save(commit=False)
          self.assertEqual(doc.myfile.name, 'something.txt')
          form = DocumentForm(instance=doc)
 
</s> remove         self.assertIn('myfile-clear', six.text_type(form))
 </s> add         self.assertIn('myfile-clear', str(form)) </s> remove         self.assertEqual(six.text_type(instance), 'Bob Woodward is 65')
 </s> add         self.assertEqual(str(instance), 'Bob Woodward is 65') </s> remove             'writer': six.text_type(self.w_woodward.pk),
 </s> add             'writer': str(self.w_woodward.pk), </s> remove         if isinstance(self.remote_field.model, six.string_types):
 </s> add         if isinstance(self.remote_field.model, str): </s> remove             six.text_type(f),
 </s> add             str(f),
        self.assertIn('name="myfile"', str(form))
        self.assertNotIn('myfile-clear', str(form))
                  model = Document
                  fields = '__all__'
  
          form = DocumentForm()
        self.assertIn('name="myfile"', str(form))
        self.assertNotIn('myfile-clear', str(form))
        self.assertIn('name="myfile"', str(form))
        self.assertNotIn('myfile-clear', str(form))
          form = DocumentForm(files={'myfile': SimpleUploadedFile('something.txt', b'content')})
          self.assertTrue(form.is_valid())
          doc = form.save(commit=False)
          self.assertEqual(doc.myfile.name, 'something.txt')
          form = DocumentForm(instance=doc)
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_forms/tests.py