private function connection_open_fail($msg='') {
		$logline = sprintf('Redis: %s connection failed',
			$this->redistype);
		if ($msg)
			$logline .= ': ' . $msg;
		$logline .= ' <- ' . json_encode($this->verified_params);
		self::$logger->error($logline);
		throw new RedisError(RedisError::CONNECTION_ERROR,
			$logline);
	}