Combine the functionality of test_support.run_unittest()
and test_support.run_classtests() into run_unittest()
and use it wherever possible.

Also don't use "from test.test_support import ...", but
"from test import test_support" in a few spots.

From SF patch #662807.
diff --git a/Lib/test/test_pickle.py b/Lib/test/test_pickle.py
index 9cfb9b7..585644e 100644
--- a/Lib/test/test_pickle.py
+++ b/Lib/test/test_pickle.py
@@ -62,12 +62,11 @@
         return u.load()
 
 def test_main():
-    loader = unittest.TestLoader()
-    suite = unittest.TestSuite()
-    suite.addTest(loader.loadTestsFromTestCase(PickleTests))
-    suite.addTest(loader.loadTestsFromTestCase(PicklerTests))
-    suite.addTest(loader.loadTestsFromTestCase(PersPicklerTests))
-    test_support.run_suite(suite)
+    test_support.run_unittest(
+        PickleTests,
+        PicklerTests,
+        PersPicklerTests
+    )
     test_support.run_doctest(pickle)
 
 if __name__ == "__main__":