Issue #19234: Documents socket.fileno() returns -1 on failure
diff --git a/Doc/library/socket.rst b/Doc/library/socket.rst
index 8cf4dba..3aa1b13 100644
--- a/Doc/library/socket.rst
+++ b/Doc/library/socket.rst
@@ -927,14 +927,13 @@
.. method:: socket.fileno()
- Return the socket's file descriptor (a small integer). This is useful with
- :func:`select.select`.
+ Return the socket's file descriptor (a small integer), or -1 on failure. This
+ is useful with :func:`select.select`.
Under Windows the small integer returned by this method cannot be used where a
file descriptor can be used (such as :func:`os.fdopen`). Unix does not have
this limitation.
-
.. method:: socket.get_inheritable()
Get the :ref:`inheritable flag <fd_inheritance>` of the socket's file