added check for queue timeouts
added check for queue timeouts

pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io