Symfony2: exclude 4xx client errors from logging

config.yml

# Monolog (log) Configuration
monolog:
    handlers:
        main:
            type: fingers_crossed
            handler: loggly
            activation_strategy: 'mybundle.monolog.fingers_crossed.activation_strategy'
        loggly:
            type: loggly
            token: %loggly_token%
            level: error
            tag: %loggly_tag%
        file:
            type: stream
            path: "%kernel.logs_dir%/%kernel.environment%.log"
            level: info
        console:
            type: console
            bubble: false

ErrorLevelActivationStrategy.php

<?php
namespace MyBundle\Handler\FingersCrossed;

use Monolog\Handler\FingersCrossed\ErrorLevelActivationStrategy as BaseErrorLevelActivationStrategy;
use Symfony\Component\HttpKernel\Exception\HttpException;

/**
 * Activation strategy that ignores client errors (4xx)
 */
class ErrorLevelActivationStrategy extends BaseErrorLevelActivationStrategy
{
    /**
     * {@inheritdoc}
     */
    public function isHandlerActivated(array $record)
    {
        $isActivated = parent::isHandlerActivated($record);

        if (
            $isActivated
            && isset($record['context']['exception'])
            && $record['context']['exception'] instanceof HttpException
            && $record['context']['exception']->getStatusCode() >= 400
            && $record['context']['exception']->getStatusCode() <= 499
        ) {
            $isActivated = false;
        }

        return $isActivated;
    }
}

services.yml

services:
    mybundle.monolog.fingers_crossed.activation_strategy:
        class: MyBundle\Handler\FingersCrossed\ErrorLevelActivationStrategy
        arguments: ['error']