Make error message more verbose when creating a repo

[osanseviero]

I recently had some issues which could have been easily found if the error message was more verbose.

Before:

requests.exceptions.HTTPError: 400 Client Error: Bad Request for url: https://huggingface.co/api/repos/create

After:

requests.exceptions.HTTPError: 400 Client Error: Bad Request for url: https://huggingface.co/api/repos/create - Only regular characters and '-', '_', '.' accepted

[LysandreJik]

LGMT

[julien-c]

LGTM, just wondering if .json() is compute intensive, or can raise an error (if not a JSON response for instance), am assuming not to both

[osanseviero]

r.json() would already raise an error if not a json response.

In terms of speed, the method uses simplejson which is supposed to be very fast.