code: func ErrInvalidRequestSignature(signature string, err error) error {
  	return ErrorResponse{
  		Code:    http.StatusForbidden,
  		Message: fmt.Sprintf("could not validate request signature: %s", signature),
  		Errors:  []Error{Error{Message: err.Error()}},
  	}
  }
docs: // ErrInvalidRequestSignature indicates the payload could not
  // be verified with the given signature.