Run 2to3 over the Demo/ directory to shut up parse errors from 2to3 about lingering print statements.
diff --git a/Demo/tix/samples/OptMenu.py b/Demo/tix/samples/OptMenu.py
index 1d39420..2cf625a 100755
--- a/Demo/tix/samples/OptMenu.py
+++ b/Demo/tix/samples/OptMenu.py
@@ -40,7 +40,7 @@
     #        global variables "demo_opt_from" and "demo_opt_to". Otherwise
     #        the OptionMenu widget will complain about "unknown options"!
     #
-    for opt in options.keys():
+    for opt in list(options.keys()):
         from_file.add_command(opt, label=options[opt])
         to_file.add_command(opt, label=options[opt])