Add versionchanged information for mock_open.
diff --git a/Doc/library/unittest.mock.rst b/Doc/library/unittest.mock.rst
index fcd7727..13b3133 100644
--- a/Doc/library/unittest.mock.rst
+++ b/Doc/library/unittest.mock.rst
@@ -2001,6 +2001,14 @@
is insufficient, one of the in-memory filesystem packages on `PyPI
<https://pypi.python.org/pypi>`_ can offer a realistic filesystem for testing.
+ .. versionchanged:: 3.4
+ Added :meth:`~io.IOBase.readline` and :meth:`~io.IOBase.readlines` support.
+ The mock of :meth:`~io.IOBase.read` changed to consume *read_data* rather
+ than returning it on each call.
+
+ .. versionchanged:: 3.4.4
+ *read_data* is now reset on each call to the *mock*.
+
Using :func:`open` as a context manager is a great way to ensure your file handles
are closed properly and is becoming common::