Django 1.8.2 handler404 and handler500 no longer work

[simon9999]

I've been testing with DEBUG=False under 'python manage.py runserver'.
As per the dox, I have added into my ROOT url file, the required overrides:

from django.conf.urls import *
from django.contrib import admin
from django.http import HttpResponse

handler404 = 'urls.custom_handler'
handler500 = 'urls.custom_handler'

urlpatterns = [
    url(r'^apikey/', include('apikey.urls', namespace='apikey')),
    url(r'^admin/', include(admin.site.urls)),
]

def custom_handler(request):
    print '---->>>> got to here!'
    raise Exception
    return HttpResponse('<h1>Boo! - Page not found</h1>')

I have created both the default 404.html and 500.html templates in my apikey/templates directory and updated the site settings file to reflect this
and I can confirm that this default 404.html and 500.html files are indeed getting rendered, but not by my routine.

My custom handler never, ever fires when a 404 or 500 is raised.

I am at a loss as to why this has stopped working and I have been searching both the tickets DB and the net for a solution so it may well be a bug.