Merge 3.4 (issue #25605)

diff --cc Doc/library/fcntl.rst
index e0d184fd062feb1a1d9ab8c8b563c70c9eecd79d,b798f22d7fb5295cc21c98c31de4dec6b786fa5b..f8bb8340ea91918ce150e6af2ed37a94f8092acc
--- 1/Doc/library/fcntl.rst
--- 2/Doc/library/fcntl.rst
+++ b/Doc/library/fcntl.rst
@@@ -104,11 -106,13 +106,13 @@@ The module defines the following functi
     :manpage:`flock(2)` for details.  (On some systems, this function is emulated
     using :c:func:`fcntl`.)
  
+    If the :c:func:`flock` fails, an :exc:`IOError` exception is raised.
+ 
  
 -.. function:: lockf(fd, operation, [length, [start, [whence]]])
 +.. function:: lockf(fd, cmd, len=0, start=0, whence=0)
  
     This is essentially a wrapper around the :func:`~fcntl.fcntl` locking calls.
 -   *fd* is the file descriptor of the file to lock or unlock, and *operation*
 +   *fd* is the file descriptor of the file to lock or unlock, and *cmd*
     is one of the following values:
  
     * :const:`LOCK_UN` -- unlock