I had this same problem with Dusty. They naturally outgrow it but if you need to take immediate action then here is what I did. After the kitty pottied and it was smelling real ripe and interesting to Dusty, I put a dab of hot sauce on it and then let him "GO FOR IT". He learned real quick after the second taste of the hot sauce that this was not something that tasted as good as it smelled.

Make sure you have water available though. He headed straight for the water bowl!

I know this is agressive and not positive training either but I just couldn't stand him eating cat poop and didn't know how to reward him for eating it or not eating it.