private function triggerKernelError()
    {
        $msgErrorSuffix = 'setting will be ignored because Kernel had been set previously.';
        if (isset($this->container)) {
            trigger_error('Container '.$msgErrorSuffix);
        }
        if (isset($this->env)) {
            trigger_error('Env '.$msgErrorSuffix);
        }
        if (isset($this->kernelClass)) {
            trigger_error('Kernel class '.$msgErrorSuffix);
        }
    }