Fix some mentions of IOError
diff --git a/Doc/library/urllib.request.rst b/Doc/library/urllib.request.rst
index 825398b..c08cbc6 100644
--- a/Doc/library/urllib.request.rst
+++ b/Doc/library/urllib.request.rst
@@ -1172,7 +1172,7 @@
*key_file* and *cert_file* are supported to provide an SSL key and certificate;
both are needed to support client authentication.
- :class:`URLopener` objects will raise an :exc:`IOError` exception if the server
+ :class:`URLopener` objects will raise an :exc:`OSError` exception if the server
returns an error code.
.. method:: open(fullurl, data=None)