"Pluggable Transport process terminated" but Tor keeps on going (and of course doesn't work)

In https://trac.torproject.org/projects/tor/ticket/33336#comment:20 I encountered the unfortunate situation where my snowflake client exited:

Feb 25 14:36:24.458 [warn] Pluggable Transport process terminated with status code 512

It still remains unclear whether snowflake had a bug that crashed it, or if Tor has a bug that made it close the socket to snowflake.

But either way, after this event Tor quietly cries to itself:

Feb 25 14:36:44.825 [warn] The connection to the SOCKS5 proxy server at 127.0.0.1:45527 just failed. Make sure that the proxy server is up and running.

and Tor Browser has no idea this is happening, or that trying to use Tor is now hopeless.

We should figure out something smarter that Tor should do in this situation. Perhaps it should exit, forcing the user to notice? Perhaps it should emit an event that Tor Browser picks up on? Maybe we have an even better idea?