e.g. https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/ios-simulator/37091

the build infra-failed, but milo gives no indication as to why.

the swarming task succeeded: https://chromium-swarm.appspot.com/task?id=3fc55c8c60275810

I think the only current way to see the cause of failure is through the buildbucket api: https://apis-explorer.appspot.com/apis-explorer/?base=https://cr-buildbucket.appspot.com/_ah/api#p/buildbucket/v1/buildbucket.get?id=8936173240406793200&_h=1&

... which, in result_details_json, shows

  \"error\": {\"message\": \"build-run-result.json returned by the swarming task is bad: >= 1 MB.\"}

Sheriffs would never be able to find this, and I suspect it'd take CCI troopers a while to do so as well. It'd be great if we could better surface the cause of failure on the build page.