code: def get_build_config_by_labels(self, label_selectors):
          
          items = self.get_all_build_configs_by_labels(label_selectors)
  
          if not items:
              raise OsbsException(
                  "Build config not found for labels: %r" %
                  (label_selectors, ))
          if len(items) > 1:
              raise OsbsException(
                  "More than one build config found for labels: %r" %
                  (label_selectors, ))
  
          return items[0]
docs: Returns a build config matching the given label
          selectors. This method will raise OsbsException
          if not exactly one build config is found.