Per http://doc/1ZyozTa907IJqw7QJNHaWIQ07v0szpUOzdLG2K6cURII and https://chromium.googlesource.com/chromiumos/platform/tast/+/HEAD/docs/test_attributes.md, my intent is for failures in tests with the "informational" attribute to not bother tree guardians, i.e. they shouldn't run inline on -release, -paladin, and -pfq builders.

However, betty-release is a bit different from other -release builders since it doesn't run against DUTs in the lab. Tast doesn't get wrapped in an Autotest test there; instead, there's a special TastVMTest stage that runs the tast command directly in a VM.

config/chromeos_config.py in chromite currently adds a tast_vm_canary_tests stage using the expression '(!disabled)', which matches informational tests in addition to non-informational ones. This results in sheriffs getting nagged about informational failures like the one in  issue 865117 .

I should probably update TastVMTest and TastVMTestStage to support a warn_only attribute like what VMTest uses. Then we can have two Tast stages on betty-release, one that runs informational tests with warn_only=True and another that runs non-informational tests with warn_only=False.