convert shebang lines: python -> python3
diff --git a/Demo/scripts/unbirthday.py b/Demo/scripts/unbirthday.py
index af58f8f..b3c7d23 100755
--- a/Demo/scripts/unbirthday.py
+++ b/Demo/scripts/unbirthday.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 # Calculate your unbirthday count (see Alice in Wonderland).
 # This is defined as the number of days from your birth until today