Celtic have faced Manchester City three times over the years and have yet to suffer a defeat to the English Premier League club. Granted, the victory over Pep Guardiola’s side on the US Tour this summer was just a friendly but Celtic did still have to face the likes of Erling Haaland and Jack Grealish to earn that win. However, it was in the competitive games in the Champions League in 2016 that the Scottish champions piled pressure on the Man City manager. In a new book called The Pep Revolution by Marti Perarnau that is due to be released this week, the writer details how Guardiola and his c…