Updated doc links to point to Python 3 documentation

docs/ref/contrib/auth.txt

@@ -279,8 +279,7 @@ Anonymous users
     * :meth:`~django.contrib.auth.models.User.set_password()`,
       :meth:`~django.contrib.auth.models.User.check_password()`,
       :meth:`~django.db.models.Model.save` and
-      :meth:`~django.db.models.Model.delete()` raise
-      :exc:`~exceptions.NotImplementedError`.
+      :meth:`~django.db.models.Model.delete()` raise :exc:`NotImplementedError`.
 
 In practice, you probably won't need to use
 :class:`~django.contrib.auth.models.AnonymousUser` objects on your own, but

docs/ref/contrib/sites.txt

@@ -474,7 +474,7 @@ method takes an :class:`~django.http.HttpRequest` object. It's able to deduce
 the ``domain`` and ``name`` by looking at the request's domain. It has
 ``save()`` and ``delete()`` methods to match the interface of
 :class:`~django.contrib.sites.models.Site`, but the methods raise
-:exc:`~exceptions.NotImplementedError`..
+:exc:`NotImplementedError`.
 
 ``get_current_site`` shortcut
 =============================