### Please describe the problem.

Git annex's special S3 remote doesn't seem to work with DRA buckets in Google cloud storage.

### What steps will reproduce the problem?

I created a DRA-style bucket in Google cloud storage:
        
    gsutil mb gs://gitannex-dra

Then followed [this hint](https://gist.github.com/jterrace/4576324) to
set up use of GCS. Except that it didn't work:

    git annex initremote gcs type=S3 encryption=none host=storage.googleapis.com port=80 bucket=gitannex-dra
    initremote gcs (checking bucket...) git-annex: Invalid argument.

### What version of git-annex are you using? On what operating system?

Wheezy, git-annex version: 5.20141024~bpo70+1

### Please provide any additional information below.

There didn't seem to be any extra logs and `--debug` didn't seem to add anything useful.
