If you’re planning on going to a concert on Arcade Fire’s upcoming arena tour, make sure you have your Sunday’s best ready. Fans who have already purchased tickets may have noticed this notification in the fine print: Please Note: NIGHT OF SHOW: Please wear formal attire or costume. The band also recently tweeted before a show in Montreal that the dress rule was mandatory. According to NME, at a Nov. 11 show, in which the audience was notified before attending that if they didn’t have on a costume than they needed to wear “formal wear or fancy dress”, frontman Win Butler addressed some of the grumblings fans posted to Twitter prior to the concert: “To anyone who felt uncomfortable dressing up–I’m not sorry” …