convert shebang lines: python -> python3
diff --git a/Demo/tkinter/guido/canvasevents.py b/Demo/tkinter/guido/canvasevents.py
index aeb0eb1..e5d27cc 100644
--- a/Demo/tkinter/guido/canvasevents.py
+++ b/Demo/tkinter/guido/canvasevents.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 from tkinter import *
 from Canvas import Oval, Group, CanvasText