http://chriskief.com/2013/09/18/django-compressor-offlinegenerationerror-and-500-html-handler500/

handler.py

from django.views.generic import TemplateView


class Handler500(TemplateView):

    template_name = '500.html'

    @classmethod
    def as_error_view(cls):
        v = cls.as_view()

        def view(request):
            r = v(request)
            r.render()
            return r

        return view
    
    # must also override this method to ensure the 500 status code is set
    def get(self, request, *args, **kwargs):
        context = self.get_context_data(**kwargs)
        return self.render_to_response(context, status=500)