updatetrackers, a more sophisticated blocker tracker script
    
    This replaces create-trackers.sh, which could only create the
    tracker bugs for a new release. updatetrackers does the whole
    tracker housekeeping process. It's intended to be run when a
    release is finalized. It closes the trackers for that release
    and removes the 'dynamic' aliases from them, moves the dynamic
    aliases to the trackers for the next release, creates the
    trackers for the next-but-one release, and updates the bug
    tables in the wiki page. It requires the bugzilla and mwclient
    Python modules.