I have a similar requirement but in my case, after all the files are uploaded, the latest one has to be uploaded in S3 , I have created a RUF with input Paramaters BucketName,Keyname and File name.
For Keyname parameter, I am passing "pyAttachStream" . I am getting an exception. Is it possible to upload only latest attachment to s3 by using the Base64 encoded pyAttachStream? If no, could you please specify any alternate approach.