I start a subprocess in a seperate thread (25 concurrent 
threads)
in some of the threads the following error occurs
 
Exception in thread Thread-4:
Traceback (most recent call last):
  File "C:\Python24\lib\threading.py", line 442, in 
__bootstrap
    self.run()
  File "upgrade.py", line 45, in run
    returncode = p.wait()
  File "C:\Python24\lib\subprocess.py", line 765, in wait
    _active.remove(self)
ValueError: list.remove(x): x not in list
 
this is the code that starts the subprocess and where I 
wait for the result
 
p = subprocess.Popen('command', \
                             stdin=None, 
stdout=subprocess.PIPE, \
                             stderr=subprocess.STDOUT, 
universal_newlines=True)
returncode = p.wait()
errormessage = p.stdout.readlines()