Same namespaces alloved in build-time

Namespace duplicity collisions are checked only on runtime ,showing warning like

2017-04-21 08:35:27.789 CEST [main] WARN o.o.y.y.p.util.ModuleDependencySort - Error while sorting module [vpp-routing-ra, Wed Mar 15 00:00:00 CET 2017]: module with same namespace (urn:ietf:params:xml:ns:yang:vpp-routing) already loaded: [vpp-routing, Wed Dec 14 00:00:00 CET 2016]

But if such combination is invalid(according to yangtools team it is) , it should fail at build time, not just show some warning in runtime