Comment 0 for bug 1551977

When using PKI, there are certain cases the user.Token constructor is called with the default __init__ value of None. The _is_pki_token passes None for the token on to the Keystone client, and an unexpected error occurs:

2016-02-25 00:35:38.979840 Failed to create user from domain scoped token.

If the token is None, we know it's not pki and should not make an extra call to the Keystone client to check.