'Create and save a new request token.
:param request: An oauthlib.common.Request object.
:param credentials: A dict of extra token credentials.
:returns: The token as an urlencoded string.'

def create_request_token(self, request, credentials):

    token = {u'oauth_token': self.token_generator(), u'oauth_token_secret': self.token_generator(), u'oauth_callback_confirmed': u'true'}
    token.update(credentials)
    self.request_validator.save_request_token(token, request)
    return urlencode(token.items())
