def acquire_nix(lock_file):  # pragma: no cover
    """Acquire a lock file on linux or osx."""
    fd = os.open(lock_file, OPEN_MODE)

    try:
        fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
    except (IOError, OSError):
        os.close(fd)
    else:
        return fd
Acquire a lock file on linux or osx.