docs: def get_group_id(groupname):
      """
      Returns the group id to a given group name. Returns ``None`` if the group does not exist.
  
      :param groupname: Group name.
      :type groupname: unicode
      :return: Group id.
      :rtype: int
      """
      gid = single_line_stdout('id -g {0}'.format(groupname), expected_errors=(1,), shell=False)
      return check_int(gid)