Patch# 1258 by Christian Heimes: kill basestring.
I like this because it makes the code shorter! :-)
diff --git a/Lib/distutils/command/install.py b/Lib/distutils/command/install.py
index f1ebcbf..b768663 100644
--- a/Lib/distutils/command/install.py
+++ b/Lib/distutils/command/install.py
@@ -449,7 +449,7 @@
             self.extra_path = self.distribution.extra_path
 
         if self.extra_path is not None:
-            if isinstance(self.extra_path, basestring):
+            if isinstance(self.extra_path, str):
                 self.extra_path = self.extra_path.split(',')
 
             if len(self.extra_path) == 1: