Python Software Foundation's Infrastructure commitee put out a call for trackers (bug/request/issue/ticket trackers) in June 2006 in order to evaluate alternatives to SourceForge for use by the Python development team. A copy of that request can be found at OriginalCallForTrackers.
Jira was the first choice of the committee. A lot of people complained about using a closed-source and hosted bug tracker, so a call was posted for volunteers to help administer a Roundup installation. Enough volunteers came forward, so work is now proceeding on improving the conversion to Roundup.
The Roundup bug tracker that serves http://bugs.python.org/ is actually hosted at http://psf.upfronthosting.co.za/roundup/tracker/
Bugs found in the living installation of Roundup for Python bugs are reported to meta-tracker -- is at http://psf.upfronthosting.co.za/roundup/meta/ Please report problems with the bug tracker there.