code: def refresh(self, *args, **kwargs):
          
          r = self.local_renderer
          packager = self.packager
          if packager == APT:
              r.sudo('DEBIAN_FRONTEND=noninteractive apt-get -yq update --fix-missing')
          elif packager == YUM:
              raise NotImplementedError
              #return upgrade_yum(*args, **kwargs)
          else:
              raise Exception('Unknown packager: %s' % (packager,))
docs: Updates/upgrades all system packages.