Comment 2 for bug 1690992

it took a good deal of effort to validate this, beyond what's in the test case, because it turns out that there are no units in the default desktop install at all that pull in network-online.target; so I had to create /etc/rc.local and modify /lib/systemd/system/rc-local.service.d/debian.conf to include 'Wants=network-online.target' see anything worth looking at (and the latter is probably also a bug in that unit). But ultimately, I've managed to get to the following state:

$ systemctl status NetworkManager-wait-online.service
● NetworkManager-wait-online.service - Network Manager Wait Online
   Loaded: loaded (/lib/systemd/system/NetworkManager-wait-online.service; enabl
   Active: failed (Result: exit-code) since Fri 2017-05-26 00:06:03 PDT; 4min 3
     Docs: man:nm-online(1)
 Main PID: 786 (code=exited, status=1/FAILURE)

May 26 00:05:32 ubuntu17 systemd[1]: Starting Network Manager Wait Online...
May 26 00:06:03 ubuntu17 systemd[1]: NetworkManager-wait-online.service: Main pr
May 26 00:06:03 ubuntu17 systemd[1]: Failed to start Network Manager Wait Online
May 26 00:06:03 ubuntu17 systemd[1]: NetworkManager-wait-online.service: Unit en
May 26 00:06:03 ubuntu17 systemd[1]: NetworkManager-wait-online.service: Failed
$ systemctl status network-online.target
● network-online.target - Network is Online
   Loaded: loaded (/lib/systemd/system/network-online.target; static; vendor pre
   Active: active since Fri 2017-05-26 00:06:03 PDT; 12min ago
     Docs: man:systemd.special(7)
           http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget

May 26 00:06:03 ubuntu17 systemd[1]: Reached target Network is Online.
$

So NetworkManager-wait-online is run, and even though I've configured this system such that the network fails to come up at boot, the network-online target is still reached after a delay.