convert shebang lines: python -> python3
diff --git a/Demo/tkinter/guido/newmenubardemo.py b/Demo/tkinter/guido/newmenubardemo.py
index 51c4e64..09ac566 100644
--- a/Demo/tkinter/guido/newmenubardemo.py
+++ b/Demo/tkinter/guido/newmenubardemo.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 """Play with the new Tk 8.0 toplevel menu option."""