Think we need to decide on an import style and stick with it everyone since now its fairly inconsistent.  I am not a big fan of using a parenthesis for importing like this so imo it is either between explicitly importing what you need (one per line)

    from oauthlib.oauth2.rfc6749.errors import UnsupportedGrantTypeError
    from oauthlib.oauth2.rfc6749.errors import InvalidClientError

or to import the module only and prefix with that

    from oauthlib.oauth2.rfc6749 import errors

I don't feel strongly about either. The former makes it very obvious what methods are used, the latter is less code and is arguably better for dynamic inspection.

@masci thoughts?