OS: Gentoo Linux 2.6.12-r6
Python: 2.5 r25:51908

When creating a Popen object that refers to a file that does not exist, the pipes that are created are not closed, and remain in the system. In long-running processes, this will eventually use up all the file descriptors available.

>> import os, subprocess
>> os.system('/usr/sbin/lsof | grep python | grep -i pipe')
...
python    18822 jfrancis    6r     FIFO        0,5               56188 pipe
python    18822 jfrancis    7r     FIFO        0,5               56190 pipe
>> p = subprocess.Popen('doesnotexist', stdout=subprocess.PIPE)
OSError: [Errno 2] No such file or directory
>> os.system('/usr/sbin/lsof | grep python | grep -i pipe')
...
python    18822 jfrancis    6r     FIFO        0,5               56188 pipe
python    18822 jfrancis    7r     FIFO        0,5               56190 pipe
python    18822 jfrancis    8r     FIFO        0,5               56713 pipe

this is duplicated to issue 5179 and is fixed in trunk