buildbot ticket 2451

2013-02-15 14:51:02-0800 [Broker,36,17.202.80.187] Unhandled Error
        Traceback (most recent call last):
          File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/twisted/internet/selectreactor.py", line 155, in _doReadOrWrite
            self._disconnectSelectable(selectable, why, method=="doRead")
          File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/twisted/internet/posixbase.py", line 260, in _disconnectSelectable
            selectable.readConnectionLost(f)
          File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/twisted/internet/tcp.py", line 257, in readConnectionLost
            self.connectionLost(reason)
          File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/twisted/internet/tcp.py", line 277, in connectionLost
            protocol.connectionLost(reason)
        --- <exception caught here> ---
          File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/twisted/spread/pb.py", line 645, in connectionLost
            notifier()
          File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/twisted/spread/pb.py", line 1341, in maybeLogout
            fn()
          File "/Library/Python/2.7/site-packages/buildbot-0.8.7p1-py2.7.egg/buildbot/pbmanager.py", line 160, in <lambda>
            return (pb.IPerspective, persp, lambda: persp.detached(mind))
          File "/Library/Python/2.7/site-packages/buildbot-0.8.7p1-py2.7.egg/buildbot/buildslave.py", line 736, in detached
            AbstractBuildSlave.detached(self, mind)
          File "/Library/Python/2.7/site-packages/buildbot-0.8.7p1-py2.7.egg/buildbot/buildslave.py", line 475, in detached
            self.botmaster.master.status.slaveDisconnected(self.slavename)
          File "/Library/Python/2.7/site-packages/buildbot-0.8.7p1-py2.7.egg/buildbot/status/master.py", line 377, in slaveDisconnected
            t.slaveDisconnected(name)
          File "/Library/Python/2.7/site-packages/buildbot-0.8.7p1-py2.7.egg/buildbot/status/status_push.py", line 323, in slaveDisconnected
            self.push('slaveDisconnected', slavename=slavename)
          File "/Library/Python/2.7/site-packages/buildbot-0.8.7p1-py2.7.egg/buildbot/status/status_push.py", line 234, in push
            self.queue.pushItem(packet)
          File "/Library/Python/2.7/site-packages/buildbot-0.8.7p1-py2.7.egg/buildbot/status/persistent_queue.py", line 284, in pushItem
            item = self.secondaryQueue.pushItem(item)
          File "/Library/Python/2.7/site-packages/buildbot-0.8.7p1-py2.7.egg/buildbot/status/persistent_queue.py", line 170, in pushItem
            raise IOError('%s already exists.' % path)
        exceptions.IOError: events_myserver.com/154 already exists.