Sealing sub-system error handling mechanism!

[ipfsunion-k]

NOT a problem actually.

Just to want to know how sealing sub-system handle errors?
I'm reading the source code related storage market, regarding to this implementation,
I have a question, after HandOff(), storage miner will froward the deal to mining-subsystem.
but how sealing sub-system to return the sealing result to storage client, I look through source code ,
but can NOT find. I suppose that CronActor handle it with start & end epoch, but can NOT know exactly error reason.
Would you please help to figure it out? thx in advance!

Best regards, Kim