title: docker registry failing due to invalid bucket name
body: <p>I am setting up a docker registry with s3.    </p>
  
  <p>With keys something like: </p>
  
  <pre><code>s3_access_key: _env:AWS_KEY
  s3_secret_key: _env:AWS_SECRET
  s3_bucket: some-bucket-name
  </code></pre>
  
  <p>however, it it fails every every time saying that upper case is now allowed in bucket names. </p>
  
  <pre><code>  File "/usr/local/lib/python2.7/dist-packages/boto/s3/connection.py", line 58, in check_lowercase_bucketname
      raise BotoClientError("Bucket names cannot contain upper-case " \
  BotoClientError: BotoClientError: Bucket names cannot contain upper-case characters when using either the sub-domain or virtual hosting calling format.
  </code></pre>
  
  <p>Any ideas? </p>