It’s a return to the Champions League for Celtic on Tuesday night as they travel to play Borussia Dortmund at the iconic Signal Iduna Park. After punishing Slovan Bratislava with a 5-1 scoreline on matchday one, there’s genuine excitement about what the Bhoys can produce despite the big step up in the quality of their opponent. Everyone knows that Dortmund will be by far the most difficult test of Celtic’s season so far. Nine wins from nine is impressive form but Brendan Rodgers’ side are playing away to last term’s Champions League finalists. Rodgers doesn’t appear to care about reputation. H…