Ability to specify "retry" on some(?) | all(?) error exit statuses

Option to re-queue a task N times when it exits in TIMEDOUT, or any combo of statuses of my choosing. Specifically, PPY has this issue for search insertion.

I dunno -- maybe it's just all non-success error statuses. PPY maybe shouldn't use the task exit status to indicate "something has errored but it should be ignored."
