KIM HARRISBERG WHEN Sidney Beukes got his bus driver's licence, he never imagined himself behind the wheel of a 40-year-old school bus that has been turned into a mobile grocery store serving low-income residents of Johannesburg. The bus is not an easy drive: there is no power steering and it chugs along. But Beukes said every time a customer climbs aboard to buy groceries they could not afford in the shops, he is reminded of why he would not want to drive anything else. "We're here for them, when people are stuck without food and it's been a tough month…