convert shebang lines: python -> python3
diff --git a/Demo/turtle/tdemo_paint.py b/Demo/turtle/tdemo_paint.py
index 337a57c..68058ab 100644
--- a/Demo/turtle/tdemo_paint.py
+++ b/Demo/turtle/tdemo_paint.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python3
 """       turtle-example-suite:
 
             tdemo_paint.py