Sigul calls session.krb_login(), but this call is deprecated (https://pagure.io/koji/issue/1906)
session.krb_login()
The quickest fix is to use session.gssapi_login() instead, but ideally we would call a higher-level method like activate_session() instead to abstract away the ssl-vs-kerberos handling code inside sigul.
session.gssapi_login()
activate_session()
A draft PR for this is in #9. I'll try to test this at some point and then merge it.