Don't allow access to Order Form for executed purchase batch

tailbone/views/purchases/batch.py

@@ -253,6 +253,8 @@ class PurchaseBatchView(BatchMasterView):
         View for editing a purchase batch as an order form.
         """
         batch = self.get_instance()
+        if batch.executed:
+            return self.redirect(self.get_action_url('view', batch))
         vendor = batch.vendor
         costs = Session.query(model.ProductCost)\
                        .join(model.Product)\