This will not work.  The Portal IAM user does not have permission to read from this bucket.  That is private data of the Repository Services and all clients must access it only through the public API (see PLFM-2368).  Therefore we cannot use the AmazonS3Client in the Portal.

Clients access data in S3 via per-signed URLs issued by the Repository Service.  See how the Portal both uploads and downloads wiki attachments.  Please follow the same pattern for makrdown upload and download.