If the send queue dir is moved, it can cause an exception. This should be seamless

[pcn]

To recover from an excessively large queue dir, this should be handled cleanly.

Current

2013-11-25T19:58:28.03246 25/11/2013 19:58:28 :: [console] Unhandled Error
2013-11-25T19:58:28.03249 Traceback (most recent call last):
2013-11-25T19:58:28.03250   File "/usr/local/lib/python2.7/dist-packages/twisted/application/app.py", line 402, in startReactor
2013-11-25T19:58:28.03251     self.config, oldstdout, oldstderr, self.profiler, reactor)
2013-11-25T19:58:28.03252   File "/usr/local/lib/python2.7/dist-packages/twisted/application/app.py", line 323, in runReactorWithLogging
2013-11-25T19:58:28.03253     reactor.run()
2013-11-25T19:58:28.03253   File "/usr/local/lib/python2.7/dist-packages/twisted/internet/base.py", line 1192, in run
2013-11-25T19:58:28.03254     self.mainLoop()
2013-11-25T19:58:28.03254   File "/usr/local/lib/python2.7/dist-packages/twisted/internet/base.py", line 1201, in mainLoop
2013-11-25T19:58:28.03255     self.runUntilCurrent()
2013-11-25T19:58:28.03256 --- <exception caught here> ---
2013-11-25T19:58:28.03256   File "/usr/local/lib/python2.7/dist-packages/twisted/internet/base.py", line 824, in runUntilCurrent
2013-11-25T19:58:28.03257     call.func(*call.args, **call.kw)
2013-11-25T19:58:28.03257   File "/opt/graphite/lib/carbon/client.py", line 101, in sendQueued
2013-11-25T19:58:28.03258     self._sendDatapoints(self.factory.takeSomeFromQueue())
2013-11-25T19:58:28.03258   File "/opt/graphite/lib/carbon/client.py", line 70, in _sendDatapoints
2013-11-25T19:58:28.03259     self.factory.queue_file.write(json.dumps(datapoints) + "\n")
2013-11-25T19:58:28.03261 exceptions.ValueError: I/O operation on closed file