Fixed nondeterministic ordering test failure in model_forms.

tests/model_forms/tests.py

@@ -1963,7 +1963,7 @@ class ModelMultipleChoiceFieldTests(TestCase):
         )
         article.categories.add(self.c2, self.c3)
         form = ArticleCategoriesForm(instance=article)
-        self.assertEqual(form['categories'].value(), [self.c2.slug, self.c3.slug])
+        self.assertCountEqual(form['categories'].value(), [self.c2.slug, self.c3.slug])
 
 
 class ModelOneToOneFieldTests(TestCase):