def fix_auth_url_version(auth_url):
    """Fix up the auth url if an invalid version prefix was given.

    People still give a v2 auth_url even when they specify that they want v3
    authentication. Fix the URL to say v3. This should be smarter and take the
    base, unversioned URL and discovery.
    """
    if get_keystone_version() >= 3:
        if has_in_url_path(auth_url, "/v2.0"):
            LOG.warning("The settings.py file points to a v2.0 keystone "
                        "endpoint, but v3 is specified as the API version "
                        "to use. Using v3 endpoint for authentication.")
            auth_url = url_path_replace(auth_url, "/v2.0", "/v3", 1)
	elif urlparse.urlsplit(auth_url).path.strip('/') == '':
	    auth_url = urlparse.urljoin(auth_url, "/v3")

    return auth_url