diff -r 0e438442fddf Doc/reference/simple_stmts.rst
--- a/Doc/reference/simple_stmts.rst	Fri Mar 14 21:39:18 2014 -0500
+++ b/Doc/reference/simple_stmts.rst	Sat Mar 15 12:10:43 2014 +0100
@@ -555,6 +555,29 @@

+
+Document 'from None' in raise statement doc
+---------------------------------------------
 The from clause is used for exception chaining: if given, the second expression 
+may be another exception class or instance or `None`, which will then be attached 
 to the raised exception as the :attr:`__cause__` attribute (which is writable).

+   >>> try:
+   ...     print(1 / 0)
+   ... except:
+   ...     raise RuntimeError("Something bad happened") from None
+   ...
+   Traceback (most recent call last):
+     File "<stdin>", line 4, in <module>
+   RuntimeError: Something bad happened
+
+
 A similar mechanism works implicitly if an exception is raised inside an
 exception handler: the previous exception is then attached as the new
 exception's :attr:`__context__` attribute::
      File "<stdin>", line 4, in <module>
    RuntimeError: Something bad happened
+
+.. versionchanged:: 3.3
+    :const:`None` is now permitted as ``Y`` in ``raise X from Y``
+
+.. versionadded:: 3.3
+    The ``__supress_context__`` attribute to suppress automatic display of the
+    exception context
+
+The :const:`from None` clause can be used to suppress the old exception with
+the new one for display purposes. This will set the
+:attr:`__suppress_context__` attribute to :const:`True` while leaving the old
+exception available in :attr:`__context__` for introspection when debugging::