'Authorize an httplib2.Http instance with a JWT assertion.
Unless specified, the \'aud\' of the assertion will be the base
uri of the request.
Args:
http: An instance of ``httplib2.Http`` or something that acts
like it.
Returns:
A modified instance of http that was passed in.
Example::
h = httplib2.Http()
h = credentials.authorize(h)'

def authorize(self, http):

    transport.wrap_http_for_jwt_access(self, http)
    return http
