S3 server side completions don't seem to be working

> e1ven
>
> It says it autocompletes s3 buckets, but it only seemed to using the history, not using a list of accessible buckets. I used s3 ls, and then s3 ls [bucketnames], and s3 ls s3://[bucketnames] and it wasn't autocompleting any of them.
>
> > interpeix
> >
> > I have the same issue, not bucket completion.

[Reddit Source](https://www.reddit.com/r/sysadmin/comments/3x2wns/awsshell_the_official_supercharged_aws_cli/cy14fyu)

Start by reproducing completion for `s3 ls`, `s3 ls [bucketnames]`, and `s3 ls s3://[bucketnames]` with accessible buckets. Trace the S3 completion entry point and compare it with history-based completion; done means accessible bucket names are suggested for these commands.

Written by the indexing model from the issue text.