python fail

fail.py

def shell(cmdline):
    start = time.time()
    
    outbuffer = StringIO.StringIO()
    print "asked to shell", cmdline
    subcommands = cmdline.split('|')
    subcommands = [command.strip() for command in subcommands]
    first, last, subcommands = subcommands[0], subcommands[-1], subcommands[1:-1]

    last_read, last_write = os.pipe()
    subprocess.Popen(first, stdout=last_write, shell=True, executable="/bin/bash")
    os.close(last_write)
    
    print "made command", first
    for command in subcommands:
        print "adding ", command
        next_read, next_write = os.pipe()
        subprocess.Popen(command, stdout=next_write, stdin=last_read, shell=True, executable="/bin/bash")
        os.close(next_write)
        os.close(last_read)
        last_read = next_read

    print "making last command", last
    mainread, mainwrite = os.pipe()
    main = subprocess.Popen(last, stdout=mainwrite, stdin=last_read, shell=True, executable="/bin/bash")
    os.close(mainwrite)

    print "chain output:"
    while True:
        now = time.time()
        if now - start > SHELL_TIMEOUT:
            import math
            raise ShellTimeout("'{}' timed out after {}ms".format(cmdline, math.floor(1000 * (now - start))))
        out = os.read(mainread, 1)
        sys.stdout.write(out)
        sys.stdout.flush()
        if out == '':
            break
        outbuffer.write(out)

    while main.poll() is None:
        print "waiting for {} to exit".format(last)
        main.terminate()
        main.kill()
        time.sleep(0.1)
    os.close(mainread)

    return outbuffer.getvalue()