OSError: [Errno 22] Invalid argument

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test.py", line 29, in <module>
    proc.communicate("bye\n")
  File "c:\python33\lib\subprocess.py", line 907, in communicate
    self.stdin.close()
OSError: [Errno 22] Invalid argument