The president of Mexico’s Senate smiled into the camera and flipped the lid of his red Tupperware. No costly expense account meals for me, proclaimed Martí Batres, a senior ally of President-elect Andrés Manuel López Obrador , as he took to social media to challenge legislators to embrace austerity by bringing their own packed lunches.In the lower House, another senior figure in López Obrador’s Morena Party, Mario Delgado, urged colleagues to follow his lead and bring in a thermos — a bid to save the . . .