Any step can have
on_failure tacked onto it, whose value is a second
step to execute only if the parent step fails.
The step to execute when the parent step fails. If the attached step
succeeds, the entire step is still
The following will perform the attached task only if the first one fails:
plan: - get: foo - task: unit file: foo/unit.yml on_failure: task: alert file: foo/alert.yml