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_codecs.py b/Lib/test/test_codecs.py
index d451c1b..33a62aa 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -333,13 +333,13 @@
                     raise test_support.TestFailed("Test 3.%d: %s" % (pos+1, str(e)))
 
 def test_main():
-    suite = unittest.TestSuite()
-    suite.addTest(unittest.makeSuite(UTF16Test))
-    suite.addTest(unittest.makeSuite(EscapeDecodeTest))
-    suite.addTest(unittest.makeSuite(RecodingTest))
-    suite.addTest(unittest.makeSuite(PunycodeTest))
-    suite.addTest(unittest.makeSuite(NameprepTest))
-    test_support.run_suite(suite)
+    test_support.run_unittest(
+        UTF16Test,
+        EscapeDecodeTest,
+        RecodingTest,
+        PunycodeTest,
+        NameprepTest
+    )
 
 
 if __name__ == "__main__":