The class “Symfony\Bundle\AsseticBundle\Config\AsseticResource” is
performing resource checking through ResourceInterface::isFresh(),
which is deprecated since 2.8 and will be removed in 3.0 (54 times)

堆栈(来自Symfony profiler)

BCResourceInterfaceChecker::isFresh() (called from bootstrap.PHP.cache at line 3061)
ResourceCheckerConfigCache::isFresh() (called from ResourceCheckerConfigCacheFactory.PHP at line 45)
ResourceCheckerConfigCacheFactory::cache() (called from classes.PHP at line 1328)
Router::getMatcher() (called from classes.PHP at line 1288)
Router::match() (called from classes.PHP at line 7170)
Router::match() (called from classes.PHP at line 2086)
RouterListener::onKernelRequest()
call_user_func() (called from WrappedListener.PHP at line 61)
WrappedListener::__invoke()
call_user_func() (called from classes.PHP at line 1853)
EventDispatcher::doDispatch() (called from classes.PHP at line 1771)
EventDispatcher::dispatch() (called from TraceableEventDispatcher.PHP at line 132)
TraceableEventDispatcher::dispatch() (called from bootstrap.PHP.cache at line 3178)
HttpKernel::handleRaw() (called from bootstrap.PHP.cache at line 3151)
HttpKernel::handle() (called from bootstrap.PHP.cache at line 3302)
ContainerAwareHttpKernel::handle() (called from bootstrap.PHP.cache at line 2498)
Kernel::handle() (called from app_dev.PHP at line 29)

升级我用过：

composer.phar update symfony/symfony --with-dependencies

这是我的composer.json

{
    "name": "framework/symfony","license": "proprietary","type": "project","autoload": {
        "psr-4": {
            "": "src/"
        }
    },"require": {
        "PHP": ">=5.3.9","symfony/symfony": "2.8.*","doctrine/orm": "^2.4.8","doctrine/doctrine-bundle": "~1.4","symfony/assetic-bundle": "~2.3","symfony/swiftmailer-bundle": "~2.3","symfony/monolog-bundle": "~2.4","sensio/distribution-bundle": "~4.0","sensio/framework-extra-bundle": "^3.0.2","incenteev/composer-parameter-handler": "~2.0"
    },"require-dev": {
        "sensio/generator-bundle": "~2.3"
    },"scripts": {
        "post-install-cmd": [
            "Incenteev\\ParameterHandler\\ScriptHandler::buildParameters","Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap","Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache","Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets","Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile","Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::prepareDeploymentTarget"
        ],"post-update-cmd": [
            "Incenteev\\ParameterHandler\\ScriptHandler::buildParameters","Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::prepareDeploymentTarget"
        ]
    },"config": {
        "bin-dir": "bin"
    },"extra": {
        "symfony-app-dir": "app","symfony-web-dir": "web","symfony-assets-install": "relative","incenteev-parameters": {
            "file": "app/config/parameters.yml"
        }
    }
}

怎么解决这个弃用警告？