AttributeError                            Traceback (most recent call last)
<ipython-input-16-c985c6423e2d> in <module>()
      7 #F='C:\Users\Prashant\Documents\IPython Notebooks\resources\ch06-mailboxes'
      8 F='resources/ch06-mailboxes/data/enron.mbox.json.bz2'
----> 9 r = envoy.run("bunzip2 %s" % (F,))
     10 print r.std_out
     11 print r.std_err

C:\Anaconda\lib\site-packages\envoy\core.py in run(command, data, timeout)
    166 
    167         cmd = Command(c)
--> 168         out, err = cmd.run(data, timeout)
    169 
    170         r = Response(process=cmd)

C:\Anaconda\lib\site-packages\envoy\core.py in run(self, data, timeout)
     51             self.process=process;
     52             thread.join()
---> 53         self.returncode = self.process.returncode
     54         return self.out, self.err
     55 

AttributeError: 'NoneType' object has no attribute 'returncode'