Gritty, grim and deeply nihilistic, “Sicario” is a dark and brooding thriller which examines the murky realpolitik of America’s ‘War On Drugs’ along the US/ Mexican border. Idealistic FBI Agent Kate Mercer (Emily Blunt) is recruited by a government official (Josh Brolin) and his mysterious partner (Benicio del Toro) to join an inter-agency task force tasked with tracking down an unspecified drug…