doc: Fix Broken Links

Author: justindhillon

test/functional/test_framework/netutil.py

@@ -4,7 +4,7 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Linux network utilities.
 
-Roughly based on http://voorloopnul.com/blog/a-python-netstat-in-less-than-100-lines-of-code/ by Ricardo Pascal
+Roughly based on https://web.archive.org/web/20190424172231/http://voorloopnul.com/blog/a-python-netstat-in-less-than-100-lines-of-code/ by Ricardo Pascal
 """
 
 import sys