The test failed on a buildbot, see the message below. By the way, the test should use a value based on test.support.PIPE_MAX_SIZE rather than an hardcoded size of 2**20 bytes.


http://buildbot.python.org/all/builders/x86%20Windows%20Server%202008%20%5BSB%5D%203.x/builds/1661/steps/test/logs/stdio

test_communicate_epipe (test.test_subprocess.ProcessTestCase) ... ERROR
test_communicate_epipe_only_stdin (test.test_subprocess.ProcessTestCase) ... ok


======================================================================
ERROR: test_communicate_epipe (test.test_subprocess.ProcessTestCase)
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Traceback (most recent call last):
  File "E:\home\cpython\buildslave\x86\3.x.snakebite-win2k8r2sp1-x86\build\lib\test\test_subprocess.py", line 1095, in test_communicate_epipe
    p.communicate(b"x" * 2**20)
  File "E:\home\cpython\buildslave\x86\3.x.snakebite-win2k8r2sp1-x86\build\lib\subprocess.py", line 952, in communicate
    stdout, stderr = self._communicate(input, endtime, timeout)
  File "E:\home\cpython\buildslave\x86\3.x.snakebite-win2k8r2sp1-x86\build\lib\subprocess.py", line 1188, in _communicate
    self.stdin.write(input)
OSError: [Errno 22] Invalid argument

----------------------------------------------------------------------
(...)
test_communicate_epipe (test.test_subprocess.ProcessTestCase) ... ok
test_communicate_epipe_only_stdin (test.test_subprocess.ProcessTestCase) ... ok