Load config from command line switches.
        NOTE: Not all config is available on the command line.

def _load_command_line(self, conf_only=False):
        '''
        Load config from command line switches.
        NOTE: Not all config is available on the command line.
        '''
        # did we already parse cli (i.e. to get conf file)? don't run twice
        if self._cli_opts:
            self._update_dict(self._cli_opts)
            return
        parser = argparse.ArgumentParser()
        debug_grp = parser.add_argument_group('Debug options')
        platf_grp = parser.add_argument_group('Platform options')
        cli_options = dict((k, v) for k, v in DEFAULT_OPTS.items() if (
                       'opt' in v))
        for _, o in cli_options.items():
            group = o.pop('group', None)
            if group == 'debug':
                g = debug_grp
            elif group == 'platform':
                g = platf_grp
            else:
                g = parser
            optnames = o.pop('opt')
            # use argparse.SUPPRESS as CLI defaults so it won't parse
            #  options that weren't specified
            o['default'] = argparse.SUPPRESS
            g.add_argument(*optnames, **o)

        options = parser.parse_args()

        self._cli_opts = vars(options)
        if conf_only and 'conf' in self._cli_opts:
            self._update_dict({'conf': self._cli_opts['conf']})
            return

        self._update_dict(self._cli_opts)