repository not present in authorization header for standalone registry

In `registry/toolbox.py` within `get_repository` should the `authorization` HTTP request header be present in standalone registries? 

I'm using HTTP Basic Auth and the `authorization` header becomes: "Basic base64(username + ':' + password)", which is normal. I cannot find the logic that conforms to `_auth_exp` and yields a "repository" for the first match in a standalone deployment.

Perhaps for private repositories?

Either way, I'm guessing it's fine to support basic auth without a given repository? In this scenario (when requesting json) `auth.get('repository')` is a NoneType causing an exception.