 Complete the following phrase:  He was retained by Porsche for the 2015 season and again raced with Bernhard and Hartley in the renumbered No. 17 car. Webber and Hartley qualified their 919 Hybrid on pole position for the season-opening 6 Hours of Silverstone but Webber was forced to retire the car early in the race with drivetrain failure. He was on pole position at the following 6 Hours of Spa-Francorchamps and finished third after Hartley incurred a stop-and-go penalty for rejoining the track via an escape road. His team qualified second at the 