'If a lock is currently locked, it cannot be locked again.'

def test_cannotLockLocked(self):

    lockf = self.mktemp()
    firstLock = lockfile.FilesystemLock(lockf)
    self.assertTrue(firstLock.lock())
    secondLock = lockfile.FilesystemLock(lockf)
    self.assertFalse(secondLock.lock())
    self.assertFalse(secondLock.locked)
