This event will be fired when something goes wrong while cleaning up.
It has two public properties:
$exception: an object that conforms to the Exception-interface. It is highly likely that $exception->getMessage() will return more information on what went wrong.
$backupDestination: if this is null then probably something went wrong before even connecting to one of the backup destinations. If it is an instance of Spatie\Backup\BackupDestination\BackupDestination something went wrong connecting or
writing to that destination.