Long audio files with Speech API - notify about errors

[maxhr2]

I have long audio files, and as suggested here - 

https://cloud.google.com/speech-to-text/docs/async-recognize#upload_your_transcription_results_to_a_...

it writes transcription results to a bucket. Then I use Storage Event triggers to invoke a Cloud Function when the operation is successful.

But I also want to invoke a different function when the transcription operation fails.
What are my options?
Are there events from Eventarc that can notify about failure of a long-running operation in Speech API?