From Joël Léger on share.ez.no forum:

Hi,

i keep having an exception when i try to render an ezobjectrelationlist_field whith :

{{ ez_render_field( content, 'carousel') }}

i got this exception :

An exception has been thrown during the rendering of a template 
("Notice: Undefined variable: response in /vendor/ezsystems/ezpublish-kernel/eZ/Publish/Core/MVC/Symfony/Controller/Content/ViewController.php line 150" in MySiteBundle:full:home_page.html.twig at line 10.

Note that the exception is thrown by the API somewhere and probably results from another problem.