Comment 13 for bug 1737640

Ok, package available in proposed.
  Version table:
 *** 0.12.8~16.04.2 500
        500 xenial-proposed/main amd64 Packages

Confusing result right after the upgrade:
root@04-57:~# ifdown -a; ifup -a
RTNETLINK answers: File exists
Failed to bring up ens3.
root@04-57:~# ifdown ens3
ifdown: interface ens3 not configured


Now it works:root@04-57:~# ifdown -a; ifup -a

If this test is acceptable, then consider this verified for xenial.