bpo-32248: Fix test_importlib.test_open()

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Use the binary.file instead of utf-8.file to avoid issues with
Unix newlines vs Windows newlines.

https://bugs.python.org/issue32248

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My .gitattributes fix (commit 44a70e9) was not enough.

The test still fails on AMD64 Windows8.1 Non-Debug 3.x for example: http://buildbot.python.org/all/#/builders/12/builds/477

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Hum, AppVeyor failed to download dependencies:

git checkout -qf FETCH_HEAD
PCbuild\build.bat -e
Using "C:\Python36\python.exe" (found as HOST_PYTHON)
Fetching external libraries...
Fetching bzip2-1.0.6...
Fetching sqlite-3.21.0.0...
Fetching xz-5.2.2...
Traceback (most recent call last):
  File "C:\projects\cpython\PCbuild\\get_external.py", line 60, in <module>
    main()
  File "C:\projects\cpython\PCbuild\\get_external.py", line 53, in main
    verbose=args.verbose,
  File "C:\projects\cpython\PCbuild\\get_external.py", line 20, in fetch_zip
    reporthook=reporthook,
  File "C:\Python36\lib\urllib\request.py", line 248, in urlretrieve
    with contextlib.closing(urlopen(url, data)) as fp:
  File "C:\Python36\lib\urllib\request.py", line 223, in urlopen
    return opener.open(url, data, timeout)
  File "C:\Python36\lib\urllib\request.py", line 532, in open
    response = meth(req, response)
  File "C:\Python36\lib\urllib\request.py", line 642, in http_response
    'http', request, response, code, msg, hdrs)
  File "C:\Python36\lib\urllib\request.py", line 564, in error
    result = self._call_chain(*args)
  File "C:\Python36\lib\urllib\request.py", line 504, in _call_chain
    result = func(*args)
  File "C:\Python36\lib\urllib\request.py", line 756, in http_error_302
    return self.parent.open(new, timeout=req.timeout)
  File "C:\Python36\lib\urllib\request.py", line 532, in open
    response = meth(req, response)
  File "C:\Python36\lib\urllib\request.py", line 642, in http_response
    'http', request, response, code, msg, hdrs)
  File "C:\Python36\lib\urllib\request.py", line 570, in error
    return self._call_chain(*args)
  File "C:\Python36\lib\urllib\request.py", line 504, in _call_chain
    result = func(*args)
  File "C:\Python36\lib\urllib\request.py", line 650, in http_error_default
    raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 502: Bad Gateway
Fetching zlib-1.2.11...
Fetching external binaries...
Fetching openssl-bin-1.1.0f...
Fetching tcltk-8.6.6.0...
Traceback (most recent call last):
  File "C:\Python36\lib\http\client.py", line 578, in _readinto_chunked
    chunk_left = self._get_chunk_left()
  File "C:\Python36\lib\http\client.py", line 544, in _get_chunk_left
    self._safe_read(2)  # toss the CRLF at the end of the chunk
  File "C:\Python36\lib\http\client.py", line 614, in _safe_read
    raise IncompleteRead(b''.join(s), amt)
http.client.IncompleteRead: IncompleteRead(0 bytes read, 2 more expected)
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "C:\projects\cpython\PCbuild\\get_external.py", line 60, in <module>
    main()
  File "C:\projects\cpython\PCbuild\\get_external.py", line 53, in main
    verbose=args.verbose,
  File "C:\projects\cpython\PCbuild\\get_external.py", line 20, in fetch_zip
    reporthook=reporthook,
  File "C:\Python36\lib\urllib\request.py", line 277, in urlretrieve
    block = fp.read(bs)
  File "C:\Python36\lib\http\client.py", line 449, in read
    n = self.readinto(b)
  File "C:\Python36\lib\http\client.py", line 483, in readinto
    return self._readinto_chunked(b)
  File "C:\Python36\lib\http\client.py", line 594, in _readinto_chunked
    raise IncompleteRead(bytes(b[0:total_bytes]))
http.client.IncompleteRead: IncompleteRead(3308 bytes read)
Finished.
(... compilation starts but fails later ...)

I scheduled a new AppVeyor build.