Patch# 1258 by Christian Heimes: kill basestring.
I like this because it makes the code shorter! :-)
diff --git a/Lib/copy_reg.py b/Lib/copy_reg.py
index d693209..81a1e7f 100644
--- a/Lib/copy_reg.py
+++ b/Lib/copy_reg.py
@@ -114,7 +114,7 @@
             if "__slots__" in c.__dict__:
                 slots = c.__dict__['__slots__']
                 # if class has a single slot, it can be given as a string
-                if isinstance(slots, basestring):
+                if isinstance(slots, str):
                     slots = (slots,)
                 for name in slots:
                     # special descriptors