Auto merge of #2647 - kvark:pipeline-error, r=glennw
Auto merge of #2647 - kvark:pipeline-error, r=glennw

Error on missed pipeline DL

We hit this in Gecko workloads. It would be ideal to cry out louder (if not panic at all), but until the Gecko side is resolved, we should at least indicate that stuff is going off the rails.

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