constructor(path, msg, immutable) {
    msg = msg || 'Field `' + path + '` is not in schema and strict ' +
      'mode is set to throw.';
    super(msg);
    this.isImmutableError = !!immutable;
    this.path = path;
  }
Strict mode error constructor

@param {String} path
@param {String} [msg]
@param {Boolean} [immutable]
@inherits MongooseError
@api private