Chicago Mayor Lori Lightfoot was mercilessly booed off a stage during a plumbers’ union fundraiser amid fallout over the city’s vaccine mandate for municipal workers, video shows. A 25-second clip posted to Twitter shows the moment the Democratic mayor was loudly jeered Sunday as she was introduced to Plumbers Union Local 130 — the Windy City’s first union to endorse her in the 2019 runoff election. “I knew that was going to happen,” one attendee said just as the crowd drowned out Lightfoot’s introduction. “That’s f–king brutal,” one man sitting at a table said. One person at the fundraiser told...