Fixed #16079: Clarified (for real this time) how handler404 and handler500 work, and that they only work in a root URLconf.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16804 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/intro/tutorial03.txt

@@ -356,11 +356,13 @@ the list is empty.
 Write a 404 (page not found) view
 =================================
 
-When you raise :exc:`~django.http.Http404` from within a view, Django will load
-a special view devoted to handling 404 errors. It finds it by looking for the
-variable ``handler404``, which is a string in Python dotted syntax -- the same
-format the normal URLconf callbacks use. A 404 view itself has nothing special:
-It's just a normal view.
+When you raise :exc:`~django.http.Http404` from within a view, Django
+will load a special view devoted to handling 404 errors. It finds it
+by looking for the variable ``handler404`` in your root URLconf (and
+only in your root URLconf; setting ``handler404`` anywhere else will
+have no effect), which is a string in Python dotted syntax -- the same
+format the normal URLconf callbacks use. A 404 view itself has nothing
+special: It's just a normal view.
 
 You normally won't have to bother with writing 404 views. By default, URLconfs
 have the following line up top::
@@ -392,9 +394,9 @@ Four more things to note about 404 views:
 Write a 500 (server error) view
 ===============================
 
-Similarly, URLconfs may define a ``handler500``, which points to a view to call
-in case of server errors. Server errors happen when you have runtime errors in
-view code.
+Similarly, your root URLconf may define a ``handler500``, which points
+to a view to call in case of server errors. Server errors happen when
+you have runtime errors in view code.
 
 Use the template system
 =======================

docs/topics/http/urls.txt

@@ -60,6 +60,10 @@ algorithm the system follows to determine which Python code to execute:
        :class:`~django.http.HttpRequest` as its first argument and any values
        captured in the regex as remaining arguments.
 
+    5. If no regex matches, or if an exception is raised during any
+       point in this process, Django invokes an appropriate
+       error-handling view. See `Error handling`_ below.
+
 Example
 =======
 
@@ -252,6 +256,31 @@ The ``prefix`` parameter has the same meaning as the first argument to
 ``patterns()`` and is only relevant when you're passing a string as the
 ``view`` parameter.
 
+include
+-------
+
+.. function:: include(<module or pattern_list>)
+
+A function that takes a full Python import path to another URLconf module that
+should be "included" in this place.
+
+:func:`include` also accepts as an argument an iterable that returns URL
+patterns.
+
+See `Including other URLconfs`_ below.
+
+Error handling
+==============
+
+When Django can't find a regex matching the requested URL, or when an
+exception is raised, Django will invoke an error-handling view. The
+views to use for these cases are specified by two variables which can
+be set in your root URLconf. Setting these variables in any other
+URLconf will have no effect.
+
+See the documentation on :ref:`customizing error views
+<customizing-error-views>` for more details.
+
 handler404
 ----------
 
@@ -281,19 +310,6 @@ value should suffice.
 .. versionchanged:: 1.2
     Previous versions of Django only accepted strings representing import paths.
 
-include
--------
-
-.. function:: include(<module or pattern_list>)
-
-A function that takes a full Python import path to another URLconf module that
-should be "included" in this place.
-
-:func:`include` also accepts as an argument an iterable that returns URL
-patterns.
-
-See `Including other URLconfs`_ below.
-
 Notes on capturing text in URLs
 ===============================
 

docs/topics/http/views.txt

@@ -122,6 +122,8 @@ In order to use the ``Http404`` exception to its fullest, you should create a
 template that is displayed when a 404 error is raised. This template should be
 called ``404.html`` and located in the top level of your template tree.
 
+.. _customizing-error-views:
+
 Customizing error views
 =======================