I'm an Arsenal fan and I think it was a penalty and called it as it happened. The only possible argument against it I can see is perhaps Holding was nudged before, but I think that is clutching at straws given how high his hand was. Can't understand the calls for a second yellow though - not every handball, even at a penalty, has to be a YC.
Shame, as other than that key decision, Kavanagh had a decent game.