Fixed broken link on Magic Methods with new link and a brief note. The original website is down.

Author: hector12free

docs/intro/learning.rst

@@ -209,6 +209,8 @@ in Python. Magic methods are surrounded by double underscores (i.e. __init__)
 and can make classes and objects behave in different and magical ways.
 
     `A Guide to Python's Magic Methods <http://www.rafekettler.com/magicmethods.html>`_
+Note: The Rafekettler.com is currently down, you can go to their Github version directly. Here you can find a PDF version:
+    `A Guide to Python's Magic Methods (repo on GitHub) <https://github.com/RafeKettler/magicmethods>`_
 
 
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