bpo-10548: expectedFailure does not apply to fixtures (GH-23201) (#26044)

(cherry picked from commit 23ae2c3bacc167f7bbfea1846bbbc9dde63a1bfd)

Co-authored-by: Irit Katriel <iritkatriel@yahoo.com>
diff --git a/Doc/library/unittest.rst b/Doc/library/unittest.rst
index 0c29408..99c2f6e 100644
--- a/Doc/library/unittest.rst
+++ b/Doc/library/unittest.rst
@@ -597,8 +597,9 @@
 .. decorator:: expectedFailure
 
    Mark the test as an expected failure or error.  If the test fails or errors
-   it will be considered a success.  If the test passes, it will be considered
-   a failure.
+   in the test function itself (rather than in one of the :dfn:`test fixture`
+   methods) then it will be considered a success.  If the test passes, it will
+   be considered a failure.
 
 .. exception:: SkipTest(reason)