convert shebang lines: python -> python3
diff --git a/Demo/sockets/rpythond.py b/Demo/sockets/rpythond.py
index d745cc7..e244d6c 100755
--- a/Demo/sockets/rpythond.py
+++ b/Demo/sockets/rpythond.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 # Remote python server.
 # Execute Python commands remotely and send output back.