convert shebang lines: python -> python3
diff --git a/Demo/turtle/tdemo_fractalcurves.py b/Demo/turtle/tdemo_fractalcurves.py
index 247f16c..c49f8b8 100644
--- a/Demo/turtle/tdemo_fractalcurves.py
+++ b/Demo/turtle/tdemo_fractalcurves.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python3
 """      turtle-example-suite:
 
         tdemo_fractalCurves.py