code: NewGTFSError createUnregisteredError (Entity entity, NewGTFSErrorType errorType) {
          return NewGTFSError.forEntity(entity, errorType);
      }
docs: WARNING: this method creates but DOES NOT STORE a new GTFS error. It should only be used in cases where a
  collection of errors need to be temporarily held before storing in batch (e.g., waiting to store travel time zero
  errors before it is determined that the entire feed uses travel times rounded to the minute).