This is a summer of love for Chinese artist Ai Weiwei, at least in Manchester. The city, whose former mayor, Andy Burnham, is expected to become the United Kingdom’s prime minister on July 20, has made generous room for another celebrity. “Button Up!”, Ai’s largest ever site-specific show, is being held at Aviva Studios, with ads running on the city’s buses and the artist’s face fluttering on banners from lamp posts. Aviva Studios, which is run by arts organisation Factory International, has...