Email spam if queue runner loses connection to db

[Julusian]

If the queue runner pods lose connection to the db, that generates an exception.
As all unhandled exceptions send an email to the specified admin address, this can cause a lot of emails to be sent in a short space of time.

In 2017, this happened briefly, and got the site locked out of the email account it was using.

Some protection needs to be put in place to prevent this from happening in future