def query_one(self, sql, **kwargs):

        LOG.debug('SQL query one [%s@%s:%d/%s]: %s %r',
                  self._settings.username, self._settings.host,
                  self._settings.port, self._settings.database, sql, kwargs)
        with self._conn.cursor() as cursor:
            rowcount = cursor.execute(sql, kwargs)
            assert rowcount <= 0
            return cursor.fetchone()
L{reporter._ExitWrapper} causes a wrapped reporter to stop after its
dataset/ETHPy150Open MirantisWorkloadMobility/CloudFerry/cloudferry/lib/os/cloud_db.py/_ConnectionWrapper.query_one--crossover with--dataset/ETHPy150Open twisted/twisted/twisted/trial/test/test_reporter.py/ExitWrapperTests.test_stopOnFailure