[web2py] Ticket caused by Popen

[weheh]

Traceback (most recent call last):
  File "C:\web2py\gluon\main.py", line 411, in wsgibase
    session._try_store_on_disk(request, response)
  File "C:\web2py\gluon\globals.py", line 377, in _try_store_on_disk
    cPickle.dump(dict(self), response.session_file)
UnpickleableError: Cannot pickle <type '_subprocess_handle'> objects

I got the above ticket in a routine that executes
subprocess.Popen(cmd).