These are failing in both presubmit and postsubmit.

Example: https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8709004025542628929/+/u/run_test.dart_for_tool_tests_shard_and_subshard_commands/stdout

The failures started with #172316 which is a doc-only change, so that's probably not the cause.

cc @dkwingsmt @bkonyi