Taken from interviews with residents of America's poorest city, the Pulitzer-winning playwright's Sweat has new resonance in the era of Trump and SandersWhen playwright Lynn Nottage began work on Sweat, Bernie Sanders was a little-known socialist senator, Donald Trump was a reality TV host and neither had a snowball in hell's chance of reaching the White House.But Sweat, currently playing at the Arena Stage in Washin…