def _register_rp(session, url_prefix, rp_name):
    """Synchronously register the RP is paremeter.
    
    Return False if we have a reason to believe this didn't work
    """
    post_url = "{}providers/{}/register?api-version=2016-02-01".format(url_prefix, rp_name)
    get_url = "{}providers/{}?api-version=2016-02-01".format(url_prefix, rp_name)
    _LOGGER.warning("Resource provider '%s' used by this operation is not "
                    "registered. We are registering for you.", rp_name)
    post_response = session.post(post_url)
    if post_response.status_code != 200:
        _LOGGER.warning("Registration failed. Please register manually.")
        return False

    while True:
        time.sleep(10)
        rp_info = session.get(get_url).json()
        if rp_info['registrationState'] == 'Registered':
            _LOGGER.warning("Registration succeeded.")
            return True
Synchronously register the RP is paremeter.
    
    Return False if we have a reason to believe this didn't work