test_readlines consistently fails on a Mac

[takluyver]

Reproduced on Python 2.7 and 3.3:

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FAIL: test_readlines (__main__.TestCaseMisc)
Note that on some slow or heavily loaded systems that the lines
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Traceback (most recent call last):
  File "tests/test_misc.py", line 126, in test_readlines
    "readlines() did not work. page=%r" % (page,))
AssertionError: readlines() did not work. page=''

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[takluyver]

It appears that Macs drop the output from the child process shortly after being send an EOF, while Linux keeps it around for longer.