Yes, that is one thing to try which is probably how the issue happened, since this error leg is very infrequent.
The other thing I was thinking is we might be able to manually trigger this code path by removing (or moving) the neutron-keepalived-state-change script out of the way and create an HA router. I think that would trigger an exception that would delete the router and go through this path. You'd just have to watch for "Error while initializing router $id" in the l3-agent log.
I don't think this traceback is related to the change, it actually looks like this bug:
The code in OSP10 isn't exactly the same, so I'm not sure it can just be picked there, we'd have to look further.
I would have to look into that bug separately as I'm not sure that backport won't cause other problems.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.