Ah, when you said the values of the key, I thought you meant if the Sets that the keys are pointing to are empty, not the key string.  It's a bug in finagle-redis that they throw though, is that something that we can stick in this commit to fix, or do you think it would end up being a bigger task?  I think it might be clearer to say, "If any of the keys passed as params are empty, this will throw."