Delete product costs for vendor when deleting vendor.

tailbone/views/vendors/core.py

@@ -29,6 +29,7 @@ from __future__ import unicode_literals
 from rattail.db import model
 from rattail.db.model import Vendor
 
+from tailbone.db import Session
 from tailbone.views import SearchableAlchemyGridView, CrudView, AutocompleteView
 from tailbone.views.continuum import VersionView, version_defaults
 from tailbone.forms import AssociationProxyField, PersonFieldRenderer
@@ -97,6 +98,14 @@ class VendorCrud(CrudView):
                 ])
         return fs
 
+    def pre_delete(self, vendor):
+
+        # Remove all product costs.
+        q = Session.query(model.ProductCost).filter(
+            model.ProductCost.vendor == vendor)
+        for cost in q:
+            Session.delete(cost)
+
 
 class VendorVersionView(VersionView):
     """