Billionaire Elon Musk said Tuesday that his purchase of Twitter would not go ahead unless he was given assurances on the bots that he says plague the platform, further complicating his acrimonious bid for the social media giant. The chief of SpaceX as well as Tesla, Musk is currently listed by Forbes as the world’s wealthiest person, with a fortune of about $230 billion, much of it in Tesla stock.