By PALOMA GIUSTIZIERI / AFPTV / AFP Next to a wall surrounding an empty lot in central Johannesburg, a cherry picker carries a man above the street. Next to a wall surrounding an empty lot in central Johannesburg, a cherry picker carries a man above the street. He is not repairing power lines, but instead spray painting a canvas larger than a billboard with portraits of four contemporary South African musicians. Known as Dbongz, the artist is at the vanguard of a growing movement that has embraced Johannesburg’s grit to create paintings that have helped the once neglected city centre spring ba…