      def test_m2m(self):
          with self.assertNumQueries(3):
              qs = Author.objects.all().prefetch_related('favorite_authors', 'favors_me')
              favorites = [(
                  [six.text_type(i_like) for i_like in author.favorite_authors.all()],
                  [six.text_type(likes_me) for likes_me in author.favors_me.all()]
              ) for author in qs]
              self.assertEqual(
                  favorites,
                  [
                      ([six.text_type(self.author2)], [six.text_type(self.author3)]),
 
</s> remove         self.assertEqual(addresses, [[six.text_type(self.author_address)], [], []])
 </s> add         self.assertEqual(addresses, [[str(self.author_address)], [], []]) </s> remove                     ([six.text_type(self.author2)], [six.text_type(self.author3)]),
                    ([six.text_type(self.author3)], [six.text_type(self.author1)]),
                    ([six.text_type(self.author1)], [six.text_type(self.author2)])
 </s> add                     ([str(self.author2)], [str(self.author3)]),
                    ([str(self.author3)], [str(self.author1)]),
                    ([str(self.author1)], [str(self.author2)]) </s> remove         lst2 = [[six.text_type(book) for book in author.books_with_year.all()] for author in qs]
 </s> add         lst2 = [[str(book) for book in author.books_with_year.all()] for author in qs] </s> remove             lst = [[six.text_type(book) for book in author.books_with_year.all()] for author in qs]
 </s> add             lst = [[str(book) for book in author.books_with_year.all()] for author in qs] </s> remove         lst2 = [[six.text_type(author) for author in book.aged_authors.all()] for book in qs]
 </s> add         lst2 = [[str(author) for author in book.aged_authors.all()] for book in qs]
                [str(i_like) for i_like in author.favorite_authors.all()],
                [str(likes_me) for likes_me in author.favors_me.all()]
      def test_m2m(self):
          with self.assertNumQueries(3):
              qs = Author.objects.all().prefetch_related('favorite_authors', 'favors_me')
              favorites = [(
                [str(i_like) for i_like in author.favorite_authors.all()],
                [str(likes_me) for likes_me in author.favors_me.all()]
                [str(i_like) for i_like in author.favorite_authors.all()],
                [str(likes_me) for likes_me in author.favors_me.all()]
              ) for author in qs]
              self.assertEqual(
                  favorites,
                  [
                      ([six.text_type(self.author2)], [six.text_type(self.author3)]),
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/prefetch_related/tests.py