docs: function addUser(user, options) {
    if (!runningAsRoot()) return;
    if (!user) throw new Error('You must provide an username');
    options = _.opts(options, {systemUser: false, home: null, password: null, gid: null, uid: null, groups: []});
    if (userExists(user)) {
      return;
    }
    if (isPlatform('linux')) {
      _addUserLinux(user, options);
    } else if (isPlatform('osx')) {
      _addUserOsx(user, options);
    } else if (isPlatform('windows')) {
      throw new Error("Don't know how to add user in Windows");
    } else {
      throw new Error("Don't know how to add user in current platform");
    }
  }