[mythtv-users] How do I get rid of old erring jobs?

[f-myth-users at media.mit.edu]

In 0.18.1:

Since I've been experimenting with transcoding, I've built up a couple
dozen jobs that mythweb all claims to be in "Errored" state.  Some of
these are more than a week old.  Not only is this annoying to see
there, but running "mythbackend -v all" is getting tedious, since
it mentions 60-odd old jobs every single iteration (currently ten
seconds since I have the job queue set to check frequently).

How do I make these go away?  Shouldn't they have gone away on their own?