Delicious kitty litter?

I hope someone can help me out here.......My dog has recently learned how to climb the gate that leads to the bathroom that we keep the cat litter in. He now drags cat poo into the adjacent bedroom and munches on it. How the heck do we keep him out of there or discourage him from eating the litter? We can't move the litterboxes or keep them up higher (the dog can also climb the toilet next to the box to get up on the counter), this is the only place they can be. We thought about spraying the litter with green apple spray, but the cats would get it on their paws and would then refuse to clean themselves. We have one Clevercat litterbox, but one of the cats will only use the hooded, front-entry box. The dog only does it when nobody is home, so we can't catch him in the act. HELP! I'm SO tired of cleaning up cat poo :(