Result on "x86 FreeBSD 7.2 custom":
--------------------
...
[148/354] test_fileinput
[149/354] test_subprocess
[36645 refs]
[36645 refs]
...
[36647 refs]
[44034 refs]
Current thread 0x28401040:
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/subprocess.py", line 1282 in _execute_child
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/subprocess.py", line 766 in __init__
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/test/test_subprocess.py", line 687 in test_leaking_fds_on_error
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/unittest/case.py", line 387 in _executeTestPart
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/unittest/case.py", line 442 in run
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/unittest/case.py", line 494 in __call__
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/unittest/suite.py", line 105 in run
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/unittest/suite.py", line 67 in __call__
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/unittest/suite.py", line 105 in run
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/unittest/suite.py", line 67 in __call__
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/test/support.py", line 1078 in run
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/test/support.py", line 1166 in _run_suite
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/test/support.py", line 1192 in run_unittest
  File "/usr/home/db3l/buildarea/custom.bolen-freebsd7/build/Lib/test/test_subprocess.py", line 1607 in test_main
  File "./Lib/test/regrtest.py", line 1029 in runtest_inner
  File "./Lib/test/regrtest.py", line 823 in runtest
  File "./Lib/test/regrtest.py", line 649 in main
  File "./Lib/test/regrtest.py", line 1604 in <module>
program finished with exit code 1
elapsedTime=2100.157408
--------------------
http://www.python.org/dev/buildbot/all/builders/x86%20FreeBSD%207.2%20custom/builds/3

So test_subprocess does timeout (5 min) because of test_leaking_fds_on_error, it may be related to #8052. subprocess.MAXFD=655000 on FreeBSD: create a subprocess requires to call close() system calls 655,000 times and test_leaking_fds_on_error() creates 1024 subprocesses.

There is something interesting in this output: the test uses a subprocess and we only have the traceback of the parent. It may be nice to have the trace of the child process. It might be possible by sending a signal to the child process (but how can we get the list of the child processes in a C signal handler?).