Patch# 1258 by Christian Heimes: kill basestring.
I like this because it makes the code shorter! :-)
diff --git a/Lib/unittest.py b/Lib/unittest.py
index bd72d90..c590558 100644
--- a/Lib/unittest.py
+++ b/Lib/unittest.py
@@ -418,7 +418,7 @@
         self._tests.append(test)
 
     def addTests(self, tests):
-        if isinstance(tests, basestring):
+        if isinstance(tests, str):
             raise TypeError("tests must be an iterable of tests, not a string")
         for test in tests:
             self.addTest(test)