bug arises when used in celery

[benquike]

The following issue occurs when it is used with celery:

Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 801, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/threading.py", line 1073, in run
    self.function(*self.args, **self.kwargs)
  File "/home/hexfuzz/.virtualenvs/driller+/local/lib/python2.7/site-packages/fuzzer/fuzzer.py", line 34, in _handle_target
    self.target()
  File "/home/hexfuzz/.virtualenvs/driller+/local/lib/python2.7/site-packages/fuzzer/fuzzer.py", line 655, in _timer_callback
    self._stuck_callback(self)
  File "/home/hexfuzz/.virtualenvs/driller+/local/lib/python2.7/site-packages/driller/local_callback.py", line 69, in driller_callback
    proc = multiprocessing.Process(target=_run_drill, args=(self, fuzz, to_drill_path))
  File "/usr/lib/python2.7/multiprocessing/process.py", line 98, in __init__
    self._authkey = _current_process._authkey
AttributeError: 'Process' object has no attribute '_authkey'