Sabotage rexec.py.  It is not safe since the new-style classes.
diff --git a/Lib/rexec.py b/Lib/rexec.py
index b1a1427..f7aa640 100644
--- a/Lib/rexec.py
+++ b/Lib/rexec.py
@@ -180,6 +180,9 @@
         sent to standard output.
 
         """
+
+        raise RuntimeError, "This code is not secure in Python 2.2 and 2.3"
+
         ihooks._Verbose.__init__(self, verbose)
         # XXX There's a circular reference here:
         self.hooks = hooks or RHooks(verbose)