convert shebang lines: python -> python3
diff --git a/Demo/scripts/pp.py b/Demo/scripts/pp.py
index 2c948f7..87b9d8f 100755
--- a/Demo/scripts/pp.py
+++ b/Demo/scripts/pp.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 # Emulate some Perl command line options.
 # Usage: pp [-a] [-c] [-d] [-e scriptline] [-F fieldsep] [-n] [-p] [file] ...