The test case below will (on Linux here) eventually quit with "OSError:
[Errno 24] Too many open files".  I assume that some additional cleaning
up is in order.

-------------------------------------------------------------------

from subprocess import Popen, PIPE

while 1:
    try:
        Popen(['nonexisting'], stdout=PIPE, stderr=PIPE)
    except OSError, err:
        if err.errno != 2:  # ignore "no such file"
            raise