Open suitable config file.
        :return:

def setup_config(self, cfg=None):
        '''
        Open suitable config file.
        :return:
        '''
        _opts, _args = optparse.OptionParser.parse_args(self)
        configs = self.find_existing_configs(_opts.support_unit)
        if configs and cfg not in configs:
            cfg = configs[0]

        return config.master_config(self.get_config_file_path(cfg))