'Test that a DeferredFilesystemLock can be used multiple times'

def test_multipleUsages(self):

    def lockAquired(ign):
        self.lock.unlock()
        d = self.lock.deferUntilLocked()
        return d
    self.lock.lock()
    self.clock.callLater(1, self.lock.unlock)
    d = self.lock.deferUntilLocked()
    d.addCallback(lockAquired)
    self.clock.advance(1)
    return d
