psycopg/psycopg2 — pull request #13 by asvetlov (2014-04-04 20:13:36+00:00)
Title: Use python3 notation for keyword-only arguments.

Sure, python2 users can understand that form.

The current version doesn't points the fact that args are keyword-only at all.
I read it as: you can use it like
.set_session(isolation_level)
or
.set_session(readonly)
which is definitelly wrong.