When rendering a controller within a template using

\Symfony\Component\HttpKernel\Controller\ControllerReference

and the controller that is being included throws an exception then the InlineFragmentRenderer tries to clean up the output buffers (line 96) using Response::closeOutputBuffers($level, false);

The following error is thrown:
UndefinedMethodException: Attempted to call method "closeOutputBuffers" on class "Symfony\Component\HttpFoundation\Response" in /Applications/MAMP/htdocs/webapp/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Fragment/InlineFragmentRenderer.php line 96.

I only saw this error after upgrading to 2.5