Fully migrated from old boto 2.x to new boto3 library, which provides more reliable and up-to-date S3 backend. Support S3 --API-ServerSideEncryption along with 36 new API pass-through options. See API pass-through options section for complete list. Support batch delete (with delete_objects API) to delete up to 1000 files with single call. 100+ times faster than sequential deletion. Support S4CMD_O