Antoine, i made you noisy because you took care about Issue11323.
I'm at r88671 (271057c7c6f3).
I'm opening this because the buildbot URL (thanks) doesn't show
anything about sendfile(2).

12:47 ~/arena/code.extern.repos/py3k.hg $ ./python.exe -Wd -m test.test_os -r -w -v

...
test_headers (__main__.TestSendfile) ... FAIL
test_invalid_offset (__main__.TestSendfile) ... ok
test_offset_overflow (__main__.TestSendfile) ... ok
test_send_at_certain_offset (__main__.TestSendfile) ... ok
test_send_whole_file (__main__.TestSendfile) ... ok
test_trailers (__main__.TestSendfile) ... /Users/steffen/arena/code.extern.repos/py3k.hg/Lib/unittest/case.py:387: ResourceWarning: unclosed file <_io.BufferedReader name='@test_28253_tmp2'>
  function()
ok
test_set_get_priority (__main__.ProgramPriorityTests) ... ok

======================================================================
FAIL: test_headers (__main__.TestSendfile)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/steffen/arena/code.extern.repos/py3k.hg/Lib/test/test_os.py", line 1517, in test_headers
    self.assertEqual(total_sent, len(expected_data))
AssertionError: 163840 != 164352

----------------------------------------------------------------------
Ran 92 tests in 0.447s

FAILED (failures=1, skipped=10)
Traceback (most recent call last):
  File "/Users/steffen/arena/code.extern.repos/py3k.hg/Lib/runpy.py", line 160, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/Users/steffen/arena/code.extern.repos/py3k.hg/Lib/runpy.py", line 73, in _run_code
    exec(code, run_globals)
  File "/Users/steffen/arena/code.extern.repos/py3k.hg/Lib/test/test_os.py", line 1573, in <module>
    test_main()
  File "/Users/steffen/arena/code.extern.repos/py3k.hg/Lib/test/test_os.py", line 1569, in test_main
    ProgramPriorityTests,
  File "/Users/steffen/arena/code.extern.repos/py3k.hg/Lib/test/support.py", line 1187, in run_unittest
    _run_suite(suite)
  File "/Users/steffen/arena/code.extern.repos/py3k.hg/Lib/test/support.py", line 1170, in _run_suite
    raise TestFailed(err)
test.support.TestFailed: Traceback (most recent call last):
  File "/Users/steffen/arena/code.extern.repos/py3k.hg/Lib/test/test_os.py", line 1517, in test_headers
    self.assertEqual(total_send, len(expected_data))
AssertionError: 163840 != 164352