code: func Rollback(tx *gorp.Transaction, err error) error {
  	if txErr := tx.Rollback(); txErr != nil {
  		return &RollbackError{
  			Err:         err,
  			RollbackErr: txErr,
  		}
  	}
  	return err
  }
docs: // Rollback rolls back the provided transaction. If the rollback fails for any
  // reason a `RollbackError` error is returned wrapping the original error. If no
  // rollback error occurs then the original error is returned.