          if dom1 != dom2:
              standardMsg = '%s != %s' % (
                  safe_repr(dom1, True), safe_repr(dom2, True))
              diff = ('\n' + '\n'.join(difflib.ndiff(
                  six.text_type(dom1).splitlines(),
                  six.text_type(dom2).splitlines(),
              )))
              standardMsg = self._truncateMessage(standardMsg, diff)
              self.fail(self._formatMessage(msg, standardMsg))
  
      def assertHTMLNotEqual(self, html1, html2, msg=None):
 
</s> remove                     difflib.ndiff(
                        six.text_type(xml1).splitlines(),
                        six.text_type(xml2).splitlines(),
                    )
 </s> add                     difflib.ndiff(xml1.splitlines(), xml2.splitlines()) </s> remove         if isinstance(self.remote_field.model, six.string_types):
 </s> add         if isinstance(self.remote_field.model, str): </s> remove             if (isinstance(dim, six.string_types) and 'Z' in dim) or dim == 3:
 </s> add             if (isinstance(dim, str) and 'Z' in dim) or dim == 3: </s> remove         if isinstance(self.remote_field.through, six.string_types) or not self.remote_field.through._meta.managed:
 </s> add         if isinstance(self.remote_field.through, str) or not self.remote_field.through._meta.managed: </s> remove         if isinstance(self.remote_field.model, six.string_types):
 </s> add         if isinstance(self.remote_field.model, str):
                str(dom1).splitlines(), str(dom2).splitlines(),
          if dom1 != dom2:
              standardMsg = '%s != %s' % (
                  safe_repr(dom1, True), safe_repr(dom2, True))
              diff = ('\n' + '\n'.join(difflib.ndiff(
                str(dom1).splitlines(), str(dom2).splitlines(),
                str(dom1).splitlines(), str(dom2).splitlines(),
              )))
              standardMsg = self._truncateMessage(standardMsg, diff)
              self.fail(self._formatMessage(msg, standardMsg))
  
      def assertHTMLNotEqual(self, html1, html2, msg=None):
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. 
django/test/testcases.py