Stopped using django.utils.unittest in the test suite.

Refs #20680.

formtools/tests/tests.py

@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 
 import datetime
 import os
+import unittest
 import warnings
 
 from django import http
@@ -10,7 +11,6 @@ from django.contrib.formtools import preview, utils
 from django.test import TestCase
 from django.test.utils import override_settings
 from django.utils._os import upath
-from django.utils import unittest
 
 from django.contrib.formtools.tests.forms import *