X_TEST_SHARD_FAILED
Means
a test shard exited non-zero
Typical cause
registered, thrown by nothing since x test --worker was deleted. It was that flag's failure; one CI job's share of the suite is x verify --only unit --shard i/n, and a red test there or in x test is X_TEST_FAILED
Fix
delete any branch matching this code, because it never runs. Match X_TEST_FAILED, whose fix is the rerun