The error only occured once, and it was not reproduced when test_cmd_line was rerunning in verbose mode.

http://www.python.org/dev/buildbot/builders/x86 Tiger 3.x/builds/25/steps/test/logs/stdio

test test_cmd_line failed -- Traceback (most recent call last):
  File "/Users/db3l/buildarea/3.x.bolen-tiger/build/Lib/test/test_cmd_line.py", line 58, in test_q
    self.verify_valid_flag('-Qold')
  File "/Users/db3l/buildarea/3.x.bolen-tiger/build/Lib/test/test_cmd_line.py", line 49, in verify_valid_flag
    data = self.start_python(cmd_line)
  File "/Users/db3l/buildarea/3.x.bolen-tiger/build/Lib/test/test_cmd_line.py", line 34, in start_python
    p = spawn_python(*args)
  File "/Users/db3l/buildarea/3.x.bolen-tiger/build/Lib/test/script_helper.py", line 29, in spawn_python
    stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  File "/Users/db3l/buildarea/3.x.bolen-tiger/build/Lib/subprocess.py", line 694, in __init__
    self.stdin = io.open(p2cwrite, 'wb', bufsize)
OSError: [Errno 9] Bad file descriptor

Re-running test test_cmd_line in verbose mode
test_directories (test.test_cmd_line.CmdLineTest) ... ok
test_large_PYTHONPATH (test.test_cmd_line.CmdLineTest) ... ok
test_optimize (test.test_cmd_line.CmdLineTest) ... ok
test_q (test.test_cmd_line.CmdLineTest) ... ok
test_run_code (test.test_cmd_line.CmdLineTest) ... ok
test_run_module (test.test_cmd_line.CmdLineTest) ... ok
test_run_module_bug1764407 (test.test_cmd_line.CmdLineTest) ... ok
test_site_flag (test.test_cmd_line.CmdLineTest) ... ok
test_unbuffered_input (test.test_cmd_line.CmdLineTest) ... ok
test_unbuffered_output (test.test_cmd_line.CmdLineTest) ... ok
test_usage (test.test_cmd_line.CmdLineTest) ... ok
test_verbose (test.test_cmd_line.CmdLineTest) ... ok
test_version (test.test_cmd_line.CmdLineTest) ... ok

----------------------------------------------------------------------
Ran 13 tests in 3.860s

OK