Update doc for BlockingIOError and its alias in the io module
diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index 76c856e..86faa58 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -109,16 +109,8 @@
.. exception:: BlockingIOError
- Error raised when blocking would occur on a non-blocking stream. It inherits
- :exc:`IOError`.
-
- In addition to those of :exc:`IOError`, :exc:`BlockingIOError` has one
- attribute:
-
- .. attribute:: characters_written
-
- An integer containing the number of characters written to the stream
- before it blocked.
+ This is a compatibility alias for the builtin :exc:`BlockingIOError`
+ exception.
.. exception:: UnsupportedOperation