The ref made only one mistake. Clear foul by Bonucci just outside the box wasn't given and the ref thought Bonucci got the ball. The penalty calls from the Celtic manager and fans are shameless. None was even close to a penalty.
The other mistake in the match was made by the 4th official who didn't see Matri's goal. If Marchisio didn't score from the rebound, we were gonna be robbed of a clear goal.