addError(path, error) {
    if (error instanceof ValidationError) {
      const { errors } = error;
      for (const errorPath of Object.keys(errors)) {
        this.addError(`${path}.${errorPath}`, errors[errorPath]);
      }

      return;
    }

    this.errors[path] = error;
    this.message = this._message + ': ' + combinePathErrors(this);
  }
add message
@param {String} path
@param {String|Error} error
@api private