What if somehow the lock is not removed

[almarklein]

If the process somehow fails to remove the lockfile, e.g. because the process (or system) crashes, the lockfile is left in place.

~~I think that this can be dealt with simply by attempting to remove the lockfile; if the process holding the lock is still alive, this will raise an error, otherwise the lockfile is deleted and the lock can be acquired by the current process. Though perhaps I am missing something?~~ edit: That only works on Windows