[1.2.X] A few test optimizations; using native unittest where no Django-specific TestCase features are required.

Backport of r13935 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@13943 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/utils/datetime_safe.py

@@ -1,9 +1,9 @@
-from django.test import TestCase
+import unittest
 
 from datetime import date as original_date, datetime as original_datetime
 from django.utils.datetime_safe import date, datetime
 
-class DatetimeTests(TestCase):
+class DatetimeTests(unittest.TestCase):
 
     def setUp(self):
         self.just_safe = (1900, 1, 1)