convert shebang lines: python -> python3
diff --git a/Demo/tkinter/guido/tkman.py b/Demo/tkinter/guido/tkman.py
index 52b6d03..4fc0488 100755
--- a/Demo/tkinter/guido/tkman.py
+++ b/Demo/tkinter/guido/tkman.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 # Tk man page browser -- currently only shows the Tcl/Tk man pages