This is needed by: 
 - master/buildbot/status/buildset.py:47:        d = self.master.data.get(('buildset', self.id, 'buildrequest'))
 - master/buildbot/status/buildset.py:58:        d = self.master.data.get(('buildset', self.id, 'buildrequest'))
 - master/buildbot/status/mail.py:568:        d = self.master.data.get(('buildset', bsid, 'buildrequest'))

The unitest succeeds.  Which changes are neded ?