code: func NewMethodNotAllowed(method string) *HTTPError {
  	return &HTTPError{http.StatusMethodNotAllowed, errors.New(`Method is not allowed:"` + method + `"`)}
  }
docs: // NewMethodNotAllowed returns an appropriate error in the case that
  // an HTTP client uses an invalid method (i.e. a GET in place of a POST)
  // on an API endpoint.