fix: fix 'no-member' for pylint

.pylintrc

@@ -18,4 +18,3 @@ disable=fixme,
         missing-class-docstring,
         missing-function-docstring,
         no-else-return,
-        no-member,

src/sideshow/web/views/orders.py

@@ -486,9 +486,11 @@ class OrderView(MasterView):  # pylint: disable=too-many-public-methods
         * :meth:`cancel_order()`
         * :meth:`submit_order()`
         """
+        session = self.Session()
+
         # drop current batch
         self.batch_handler.do_delete(batch, self.request.user)
-        self.Session.flush()
+        session.flush()
 
         # send back to "create order" which makes new batch
         route_prefix = self.get_route_prefix()
@@ -506,8 +508,10 @@ class OrderView(MasterView):  # pylint: disable=too-many-public-methods
         * :meth:`start_over()`
         * :meth:`submit_order()`
         """
+        session = self.Session()
+
         self.batch_handler.do_delete(batch, self.request.user)
-        self.Session.flush()
+        session.flush()
 
         # set flash msg just to be more obvious
         self.request.session.flash("New order has been deleted.")