convert shebang lines: python -> python3
diff --git a/Demo/turtle/tdemo_bytedesign.py b/Demo/turtle/tdemo_bytedesign.py
index 2e2ac62..96118b3 100644
--- a/Demo/turtle/tdemo_bytedesign.py
+++ b/Demo/turtle/tdemo_bytedesign.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python3
 """      turtle-example-suite:
 
         tdemo_bytedesign.py