'Add the client credentials to the request body.
The client makes a request to the token endpoint by adding the
following parameters using the "application/x-www-form-urlencoded"
format in the HTTP request entity-body:
grant_type
REQUIRED.  Value MUST be set to "client_credentials".
scope
OPTIONAL.  The scope of the access request as described by
`Section 3.3`_.
.. _`Section 3.3`: http://tools.ietf.org/html/draft-ietf-oauth-v2-28#section-3.3'

def prepare_request_body(self, body=u'', scope=None, **kwargs):

    return prepare_token_request(u'client_credentials', body=body, scope=scope, **kwargs)
