Fix the doc: add deprecation warning in select module.

Doc/library/select.rst

@@ -377,9 +377,13 @@ linearly scanned again. :c:func:`select` is O(highest file descriptor), while
 
    Modifies an already registered fd. This has the same effect as
    ``register(fd, eventmask)``.  Attempting to modify a file descriptor
-   that was never registered causes an :exc:`IOError` exception with errno
+   that was never registered causes an :exc:`OSError` exception with errno
    :const:`ENOENT` to be raised.
 
+   .. deprecated:: 3.3
+
+      Instead of :exc:`IOError` the :exc:`OSError` exception is used now.
+
 
 .. method:: poll.unregister(fd)