convert shebang lines: python -> python3
diff --git a/Doc/includes/email-alternative.py b/Doc/includes/email-alternative.py
index 82e3ffa..33c430a 100644
--- a/Doc/includes/email-alternative.py
+++ b/Doc/includes/email-alternative.py
@@ -1,4 +1,4 @@
-#! /usr/bin/python
+#!/usr/bin/env python3
 
 import smtplib