Liberty Ross is divorcing her cheating “Snow White and the Huntsman” director husband, Rupert Sanders, who was caught on camera cavorting with actress Kristen Stewart. Ross filed divorce papers last night in Los Angeles County Superior Court, and asked for joint custody of the couple’s two children, Skyla, 7, and, Tennyson, 5. Ross — who left her job as a successful model in London to give her husband a start in Hollywood — and Sanders had tried to work things out with couples counseling after his tryst with Stewart was exposed in July. Meanwhile, we just revealed Ross has “become close” to music mogul Jimmy Iovine after being introduced by mutual friends.