bad file descriptor on windows

These kinds of errors appear when running the pyinstaller tests in parallel on appevor.

_________________________ test_chdir_meipass[onefile] _________________________
[gw0] win32 -- Python 3.6.1 c:\python36-x64\python.exe
self = <CallInfo when='call' exception: [Errno 9] Bad file descriptor>
func = <function call_runtest_hook.<locals>.<lambda> at 0x0000007B80D672F0>
when = 'call'
    def __init__(self, func, when):
        #: context of invocation: one of "setup", "call",
        #: "teardown", "memocollect"
        self.when = when
        self.start = time()
        try:
>           self.result = func()
c:\python36-x64\lib\site-packages\_pytest\runner.py:157: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
c:\python36-x64\lib\site-packages\_pytest\runner.py:145: in <lambda>
    return CallInfo(lambda: ihook(item=item, **kwds), when=when)
c:\python36-x64\lib\site-packages\_pytest\vendored_packages\pluggy.py:745: in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
c:\python36-x64\lib\site-packages\_pytest\vendored_packages\pluggy.py:339: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
c:\python36-x64\lib\site-packages\_pytest\vendored_packages\pluggy.py:334: in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
c:\python36-x64\lib\site-packages\_pytest\vendored_packages\pluggy.py:613: in execute
    return _wrapped_call(hook_impl.function(*args), self.execute)
c:\python36-x64\lib\site-packages\_pytest\vendored_packages\pluggy.py:250: in _wrapped_call
    wrap_controller.send(call_outcome)
c:\python36-x64\lib\site-packages\_pytest\capture.py:138: in pytest_runtest_call
    self.suspendcapture_item(item, "call")
c:\python36-x64\lib\site-packages\_pytest\capture.py:155: in suspendcapture_item
    out, err = self.suspendcapture(in_=in_)
c:\python36-x64\lib\site-packages\_pytest\capture.py:96: in suspendcapture
    outerr = cap.readouterr()
c:\python36-x64\lib\site-packages\_pytest\capture.py:319: in readouterr
    self.err.snap() if self.err is not None else "")
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
self = <FDCapture 2 oldfd=9>
    def snap(self):
        f = self.tmpfile
>       f.seek(0)
E       OSError: [Errno 9] Bad file descriptor
c:\python36-x64\lib\site-packages\_pytest\capture.py:365: OSError
!!!!!!!!!!!! xdist.dsession.Interrupted: stopping after 5 failu