possibly culprit https://chromium-review.googlesource.com/c/437762/

probably not.

recipe_engine.stream.StreamEngineInvariants.StepStream.write_line breaks on strings that have a newline character.
https://cs.chromium.org/chromium/infra/recipes-py/recipe_engine/stream.py?l=296

but recipes.py calls write_line with failure human_reason without escaping
https://chromium.googlesource.com/external/github.com/luci/recipes-py/+blame/9456147555cc76adec014709e02928b620d7d8d9/recipes.py#107

fix landed 23min ago https://codereview.chromium.org/2688563002/ and got rolled into build.git
https://chromium.googlesource.com/chromium/tools/build/+/master/infra/config/recipes.cfg#14

please verify

Well, the error message seems to have disappeared:

https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Ftryserver.chromium.linux%2Flinux_chromium_chromeos_rel_ng%2F361033%2F%2B%2Frecipes%2Fstderr

but there still seems to be a related failure here:

https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_chromeos_rel_ng/builds/361033

That build was started after comment #4 was posted and appears to have used build rev b3326718 which includes the recipes roll.

Unsure if it's actually the same bug. Thoughts?

This needs more attention. Still seeing failures for unclear reasons, on many CLs (not just mine). Another example:

https://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_amd64-generic_chromium_compile_only_ng/builds/278845

Actually in all cases I think perhaps the new problem is:

"Failing build because ninja reported work to do."

So perhaps there's a separate bug in that errors are not being surfaced in any visible way, so they all look like the same generic "steps" failure and you have to be lucky enough to find the meaningful cause in thousands upon thousands of log lines.

Either way, sounds like that's a separate issue, and the original bug here has been fixed.

There's a real issue here with how the "Failing build because ninja reported work to do" problem is being handled.

I'll follow up on that in bog 690269.

 bug 690269  :)