Class is back in session at “Hogwarts”, at least for visitors who are again allowed through the magical doors of the studios where much of the Harry Potter film series was filmed in Leavesden, Hertfordshire, UK. Closed since March 2020 because of the coronavirus pandemic, the Warner Bros Studio Tour London – The Making of Harry Potter reopened on August 20. Muggles and would-be wizards and witches were treated to a new attraction, “A Celebration of Slytherin”, which was built during the closure…