message: validateStatus: Add yet another possible error message attr.
  Improves many error messages in the console, such as downloading kubeconfig.
diff: @@ -46,6 +46,9 @@ const validateStatus = (response) => {
  if (!reason) {
  reason = response.statusText;
  }
  + if (!reason) {
  + reason = json.error;
  + }
  const error = new Error(reason);
  error.response = response;
  throw error;
  