'Figure out where to redirect after the \'Save\' button has been pressed
when editing an existing object.'

def response_post_save_change(self, request, obj):

    opts = self.model._meta
    if self.has_change_permission(request, None):
        post_url = reverse(('admin:%s_%s_changelist' % (opts.app_label, opts.model_name)), current_app=self.admin_site.name)
        preserved_filters = self.get_preserved_filters(request)
        post_url = add_preserved_filters({'preserved_filters': preserved_filters, 'opts': opts}, post_url)
    else:
        post_url = reverse('admin:index', current_app=self.admin_site.name)
    return HttpResponseRedirect(post_url)
