code: function userError (details = [], code) {
    const err = new Error('User error');
    err.userError = true;
    err.code = code;
    err.details = details;
    return err;
  }
docs: Creates a User Error object.
  Each error has a details array where each entry is a message line to
  be printed.
  The error is supposed to bubble up the chain and print the cli help if
  the option is enabled.
  The `userError` property can be used to know if the error is created
  on purpose rather than thrown by something else.
  
  @param {array} details The message lines
  
  @returns Error