Use Symfony 2.8.17 for tests because 2.8.18 breaks
Use Symfony 2.8.17 for tests because 2.8.18 breaks

This is due to phpunit 6.0 requirement which is only available for PHP 7

aimeos/aimeos-symfony2,aimeos/aimeos-symfony2,aimeos/aimeos-symfony,aimeos/aimeos-symfony2