We're currently running a substantially-customized router_info.py -- we need the same behavior in newton so that diff needs to be re-applied to the newton files. Unfortunately there's been a lot of change to the base file between Mitaka and Newton so it's not an easy patch.
Context for this is in T167357 and T168580; the actual changes for Mitaka are https://gerrit.wikimedia.org/r/#/c/operations/puppet/+/422474/4/modules/openstack/files/mitaka/neutron/l3/router_info.py and https://gerrit.wikimedia.org/r/#/c/operations/puppet/+/425252/