Elon Musk’s choice of Warner Bros Studios for the long-anticipated launch of his robotaxi on October 10th is entirely appropriate. Hollywood’s film studios are as much a dream factory as Tesla, his electric-car company. The vision he served up, accompanied by whoops of delight from the superfans in the audience, is an autonomous Cybercab so cheap that it will serve as “individualised mass transit”. But Mr Musk’s promises were, like…