As exhibited for instance here:
http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=spoonbill&dt=2015-05-16%2011%3A00%3A07
I've been able to replicate this on a Fedora 21 box: works fine with
Python 2, fails with Python 3. Seems like we still have an issue
with reliance on a system-provided sort method.
regards, tom lane