Clearer errors

[mduqueoviedo]

In the lib, the HttpUnauthorized error is mapped as raise Error.new("unauthorized", "Missing, invalid or expired access token.")

However I have received this error in two cases when the situation is different:

• When my developer key got a permission error, specifically when I tried to create a new figo user and my app was not authorised to do so.
• When I invoke session.user over a previously removed user (but the session is valid).

In both cases I think the problem has nothing to do with the token and the error is a bit misleading.

[homeworkprod]

That's my experience as well.