app/AppKernel.php
public function registerContainerConfiguration(LoaderInterface $loader)
    {   
        $loader->load(__DIR__.'/config/config_'.$this->getEnvironment().'.yml');

        // This small hack allows to register custom 
        // configuration files for executing tests.
        if (function_exists('registerContainerConfiguration')) {
            registerContainerConfiguration($loader);
        }
    }
public function registerContainerConfiguration(LoaderInterface $loader)
    {   
        $loader->load(__DIR__.'/config/config_'.$this->getEnvironment().'.yml');

        // This small hack allows to register custom 
        // configuration files for executing tests.
        if (function_exists('registerContainerConfiguration')) {
            registerContainerConfiguration($loader);
        }
    }
{@inheritdoc}