java1.5:File#flock returns false if trying to lock an exclusively locked file
critical(hangs):File#flock blocks if trying to lock an exclusively locked file
fails:File#flock fails with EBADF acquiring exclusive lock on read-only File
fails:File#flock fails with EBADF acquiring shared lock on read-only File
fails:File#flock blocks if trying to lock an exclusively locked file
windows:File#flock returns false if trying to lock an exclusively locked file
