[1.8.x] Refs #25693 -- Added a regression test for `to_attr` validation on forward m2m.

        self.assertIn('prefetch_related', str(cm.exception))

        self.assertIn("name", str(cm.exception))

    def test_m2m_shadow(self):

    def test_forward_m2m_to_attr_conflict(self):

        msg = 'to_attr=authors conflicts with a field on the Book model.'

        authors = Author.objects.all()

        with self.assertRaisesMessage(ValueError, msg):

            list(Book.objects.prefetch_related(

                Prefetch('authors', queryset=authors, to_attr='authors'),

            ))

        # Without the ValueError, an author was deleted due to the implicit

        # save of the relation assignment.

        self.assertEqual(self.book1.authors.count(), 3)

    def test_reverse_m2m_to_attr_conflict(self):

        msg = 'to_attr=books conflicts with a field on the Author model.'

        poems = Book.objects.filter(title='Poems')

        with self.assertRaisesMessage(ValueError, msg):