post-lock — Notification of a successful path lock.
The post-lock hook runs after one or
          more paths have been locked.  It is typically used to send
          email notification of the lock event.
If the post-lock hook returns a
          nonzero exit status, the lock will
          not be aborted since it has already
          completed.  However, anything that the hook printed
          to stderr will be marshalled back to the
          client, making it easier to diagnose hook failures.