Comment 3 for bug 1731623

I think that I found what is reason of issue. I was checking one example test in midonet: midonet.neutron.tests.unit.test_midonet_plugin_ml2.TestMidonetSubnetsML2.test_create_subnet_with_none_gateway_allocation_pool

It looks that it is failing because it tries to load Route object from os_vif.objects.route.Route instead of neutron.objects.subnet.Route and that cause problem.
IMHO patch which You are trying to revert is not reason of issue - it only triggered "real" bug but it would be great is someone more experienced with OVO could look at it also.