'Prepare an access token refresh request.
Expired access tokens can be replaced by new access tokens without
going through the OAuth dance if the client obtained a refresh token.
This refresh token and authentication credentials can be used to
obtain a new access token, and possibly a new refresh token.
:param token_url: Provider token refresh endpoint URL.
:param refresh_token: Refresh token string.
:param body: Request body (URL encoded string).
:param scope: List of scopes to request. Must be equal to
or a subset of the scopes granted when obtaining the refresh
token.
:param kwargs: Additional parameters to included in the request.
:returns: The prepared request tuple with (url, headers, body).'

def prepare_refresh_token_request(self, token_url, refresh_token=None, body=u'', scope=None, **kwargs):

    if (not is_secure_transport(token_url)):
        raise InsecureTransportError()
    self.scope = (scope or self.scope)
    body = self.prepare_refresh_body(body=body, refresh_token=refresh_token, scope=self.scope, **kwargs)
    return (token_url, FORM_ENC_HEADERS, body)
