'Return the name of the found config file or print usage/exit.'

def default_configfile(self):

    config = None
    for path in self.searchpaths:
        if os.path.exists(path):
            config = path
            break
    if ((config is None) and self.require_configfile):
        self.usage(('No    config    file    found    at    default    paths    (%s);    use    the    -c    option    to    specify    a    config    file    at    a    different    path' % ',    '.join(self.searchpaths)))
    return config
