[py3k] Silence many warnings while running the tests.

tests/modeltests/validation/test_error_messages.py

@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 
 from django.core.exceptions import ValidationError
 from django.db import models
+from django.utils import six
 from django.utils.unittest import TestCase
 
 
@@ -18,7 +19,7 @@ class ValidationMessagesTest(TestCase):
         self._test_validation_messages(f, 'fõo',
             ["'fõo' value must be an integer."])
         # primary_key must be True. Refs #12467.
-        with self.assertRaisesRegexp(AssertionError,
+        with six.assertRaisesRegex(self, AssertionError,
                 "AutoFields must have primary_key=True."):
             models.AutoField(primary_key=False)