Use `context.template.engine.debug` instead of `settings.DEBUG`

[mixxorz]

Exceptions are raised if settings.DEBUG is True. This is OK, but to be more inline with Django's recommendations, we should check the value of debug in the template engine's settings instead.

Ref: https://docs.djangoproject.com/en/3.2/topics/templates/#django.template.backends.django.DjangoTemplates