[2.1.x] Fixed #29877 -- Replaced diveintopython3.net with diveinto.org/python3/.

Backport of b0d716cb from master

AUTHORS

@@ -897,6 +897,6 @@ A big THANK YOU goes to:
 
     Ian Bicking for convincing Adrian to ditch code generation.
 
-    Mark Pilgrim for "Dive Into Python" (http://www.diveintopython3.net).
+    Mark Pilgrim for "Dive Into Python" (http://www.diveinto.org/python3/).
 
     Guido van Rossum for creating Python.

docs/intro/contributing.txt

@@ -43,7 +43,7 @@ so that it can be of use to the widest audience.
     to |django-developers| or drop by `#django-dev on irc.freenode.net`__ to
     chat with other Django users who might be able to help.
 
-__ http://www.diveintopython3.net/
+__ http://www.diveinto.org/python3/
 __ irc://irc.freenode.net/django-dev
 
 What does this tutorial cover?
@@ -333,7 +333,7 @@ This test checks that the ``make_toast()`` returns ``'toast'``.
     * After reading those, if you want something a little meatier to sink
       your teeth into, there's always the Python :mod:`unittest` documentation.
 
-__ http://www.diveintopython3.net/unit-testing.html
+__ http://www.diveinto.org/python3/unit-testing.html
 
 Running your new test
 ---------------------

docs/intro/index.txt

@@ -36,5 +36,5 @@ place: read this material to quickly get up and running.
 
     .. _python: https://python.org/
     .. _list of Python resources for non-programmers: https://wiki.python.org/moin/BeginnersGuide/NonProgrammers
-    .. _Dive Into Python: http://www.diveintopython3.net/
+    .. _Dive Into Python: http://www.diveinto.org/python3/
     .. _books about Python: https://wiki.python.org/moin/PythonBooks

docs/ref/django-admin.txt

@@ -1604,7 +1604,7 @@ Example usage::
 
     django-admin migrate --pythonpath='/home/djangoprojects/myproject'
 
-.. _import search path: http://www.diveintopython3.net/your-first-python-program.html#importsearchpath
+.. _import search path: http://www.diveinto.org/python3/your-first-python-program.html#importsearchpath
 
 .. django-admin-option:: --settings SETTINGS
 

docs/ref/templates/builtins.txt

@@ -2092,7 +2092,7 @@ individual elements of the sequence.
 Returns a slice of the list.
 
 Uses the same syntax as Python's list slicing. See
-http://www.diveintopython3.net/native-datatypes.html#slicinglists
+http://www.diveinto.org/python3/native-datatypes.html#slicinglists
 for an introduction.
 
 Example::

docs/topics/settings.txt

@@ -46,7 +46,7 @@ The value of ``DJANGO_SETTINGS_MODULE`` should be in Python path syntax, e.g.
 ``mysite.settings``. Note that the settings module should be on the
 Python `import search path`_.
 
-.. _import search path: http://www.diveintopython3.net/your-first-python-program.html#importsearchpath
+.. _import search path: http://www.diveinto.org/python3/your-first-python-program.html#importsearchpath
 
 The ``django-admin`` utility
 ----------------------------