Upload a previously-built site to LSST the Docs.

def upload_site(self):
        """Upload a previously-built site to LSST the Docs."""
        if not os.path.isdir(self._config['build_dir']):
            message = 'Site not built at {0}'.format(self._config['build_dir'])
            self._logger.error(message)
            raise RuntimeError(message)

        ltdclient.upload(self._config)