Cannot close os.pipe

Describe the bug File descriptor returned by os.pipe() cannot be closed:

_, w = os.pipe()
os.close(w)

OSError: [Errno 9] Bad file descriptor in the fake filesystem: '12'

How To Reproduce Using pytest:

import os
def test_1(fs):
    read, write = os.pipe()
    os.close(write)

Save above as test_foobar.py and run:

$ pytest -vvvv test_foobar.py 
======================================================================================= test session starts =======================================================================================
platform linux -- Python 3.6.5, pytest-4.2.1, py-1.8.0, pluggy-0.9.0 -- /service/nox/test-3-6/bin/python3.6
cachedir: .pytest_cache
rootdir: /service, inifile:
plugins: requests-mock-1.5.2, cov-2.6.1, pyfakefs-3.5.8
collected 1 item                                                                                                                                                                                  

test_foobar.py::test_1 FAILED                                                                                                                                                               [100%]

============================================================================================ FAILURES =============================================================================================
_____________________________________________________________________________________________ test_1 ______________________________________________________________________________________________

fs = <pyfakefs.fake_filesystem.FakeFilesystem object at 0x7fa25d6431d0>

    def test_1(fs):
        read, write = os.pipe()
>       os.close(write)

/service/test_foobar.py:4: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
/service/nox/test-3-6/lib/python3.6/site-packages/pyfakefs/fake_filesystem.py:3700: in close
    file_handle = self.filesystem.get_open_file(file_des)
/service/nox/test-3-6/lib/python3.6/site-packages/pyfakefs/fake_filesystem.py:1355: in get_open_file
    self.raise_os_error(errno.EBADF, str(file_des))
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pyfakefs.fake_filesystem.FakeFilesystem object at 0x7fa25d6431d0>, errno = 9, filename = '10', winerror = None

    def raise_os_error(self, errno, filename=None, winerror=None):
        """Raises OSError.
        The error message is constructed from the given error code and shall
        start with the error string issued in the real system.
        Note: this is not true under Windows if winerror is given - in this
        case a localized message specific to winerror will be shown in the
        real file system.
    
        Args:
            errno: A numeric error code from the C variable errno.
            filename: The name of the affected file, if any.
            winerror: Windows only - the specific Windows error code.
        """
        message = self._error_message(errno)
        if (winerror is not None and sys.platform == 'win32' and
                self.is_windows_fs):
            if IS_PY2:
                raise WindowsError(winerror, message, filename)
            raise OSError(errno, message, filename, winerror)
>       raise OSError(errno, message, filename)
E       OSError: [Errno 9] Bad file descriptor in the fake filesystem: '10'

/service/nox/test-3-6/lib/python3.6/site-packages/pyfakefs/fake_filesystem.py:976: OSError
==================================================================================== 1 failed in 0.71 seconds =====================================================================================

Please provide a unit test or a minimal code snippet that reproduces the problem.

Your enviroment

Linux-4.20.13-200.fc29.x86_64-x86_64-with
Python 3.6.5 (default, Aug 22 2018, 14:30:18) 
pyfakefs 3.5.8

[saml]

Currently with master, running the same test case that involves multiprocessing hangs indefinitely (or until pytest timeout). I’ll close this and patch multiprocessing.

[mrbean-bremen]

@tomhey - I added a small chapter for this kind of problems.