Share some code for validating vendor field

and add validation for new Ordering batch

tailbone/views/master.py

@@ -847,6 +847,13 @@ class MasterView(View):
         url = self.request.route_url('vendors.view', uuid=vendor.uuid)
         return tags.link_to(text, url)
 
+    def valid_vendor_uuid(self, node, value):
+        if value:
+            model = self.model
+            vendor = self.Session.get(model.Vendor, value)
+            if not vendor:
+                node.raise_invalid("Vendor not found")
+
     def render_department(self, obj, field):
         department = getattr(obj, field)
         if not department: