I found the --fail-fast option to pipetask, which causes the pipeline execution to fail immediately on error, instead of trying to continue execution. I think this is what we want for ap_verify, as it's purpose is to test our pipeline, and any failures should halt.
Adding `"--fail-fast",` to line 98 of ap_verify's pipeline_driver.py seems to have done the trick.
Alternately, we could make this a commandline option to ap_verify, if we don't want to always fail immediately (but I think we do?).