code: func ClassifyError(err error) cb.Status {
  	switch errors.Cause(err) {
  	case msgprocessor.ErrChannelDoesNotExist:
  		return cb.Status_NOT_FOUND
  	case msgprocessor.ErrPermissionDenied:
  		return cb.Status_FORBIDDEN
  	default:
  		return cb.Status_BAD_REQUEST
  	}
  }
docs: // ClassifyError converts an error type into a status code.