the bigint migration removed the foreign key constraints for:
- host_id
- job_id (and projectupdate_id, etc...)
because of this, we don't really need to check explicitly for a host_id
IntegrityError anymore (because it won't occur)
additionally, while it's possible to insert an event with a mismatched
job_id now (for example, you can totally start a long-running job, and
delete the job record in the background using the ORM or psql), doing
so results in DoesNotExist errors in the code that handles the
playbook_on_stats events
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