code: def start(self, service):
          
          try:
              map(self.start_class, service.depends)
              if service.is_running():
                  return
              if service in self.failed:
                  log.warning("%s previously failed to start", service)
                  return
              service.start()
          except Exception:
              log.exception("Unable to start service %s", service)
              self.failed.add(service)
docs: Start the service, catching and logging exceptions