The code below (from Lib/popen2.py) appears to leak no
less then 4 filedescriptors if os.fork() raises an
exception (say "OSError: [Errno 12] Not enough space"
on a Solaris box running out of swap).

Popen3.__init__() appears to leak 6 filedescriptors.

class Popen4(Popen3):
    def __init__(self, cmd, bufsize=-1):
        p2cread, p2cwrite = os.pipe()
        c2pread, c2pwrite = os.pipe()
        self.pid = os.fork()