Fix the doc: add deprecation warning in select module.
diff --git a/Doc/library/select.rst b/Doc/library/select.rst
index 4fae87e..4bf1a9f 100644
--- a/Doc/library/select.rst
+++ b/Doc/library/select.rst
@@ -377,9 +377,13 @@
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)