Symfony 3.4 Flex - `PropelDataCollector` without `reset()` method

[ldath]

Hi,

PropelBundle have issues with the Symfony 3.4 when running functional tests:

Implementing "Symfony\Component\HttpKernel\DataCollector\DataCollectorInterface" without the "reset()" method is deprecated since version 3.4 and will be unsupported in 4.0 for class "Propel\Bundle\PropelBundle\DataCollector\PropelDataCollector": 1x
    1x in DefaultControllerTest::testIndex from App\Tests\Controller