use new permission and existence decorator

jdav_web/finance/admin.py

@@ -370,13 +370,8 @@ class StatementConfirmedAdmin(admin.ModelAdmin):
 
         return render(request, 'admin/unconfirm_statement.html', context=context)
 
-    def statement_summary_view(self, request, object_id):
-        try:
-            statement = StatementConfirmed.objects.get(pk=object_id)
-        except StatementConfirmed.DoesNotExist:
-            messages.error(request, _('Statement not found.'))
-            return HttpResponseRedirect(reverse('admin:%s_%s_changelist' % (self.opts.app_label, self.opts.model_name)))
-
+    @decorate_statement_view(StatementConfirmed, perm='finance.may_manage_confirmed_statements')
+    def statement_summary_view(self, request, statement):
         if not statement.confirmed:
             messages.error(request,
                     _("%(name)s is not yet confirmed.") % {'name': str(statement)})