Retrieves a short-lived pre-signed download URL for the error file produced by an import batch that finished with a status of completed_with_errors.

The error file is the original upload reduced to only the failing rows, with the reason for each failure appended to the row. Correct the rows in this file and resubmit them using Retry import batch.

Error files expire 30 days after the batch completed. Requesting one after that returns a 422.

Note that the response body is the bare URL as a plain string rather than a JSON object, even though the Content-Type response header is application/json.