Should we disable documentation test on nntplib? It's surprising that test_nntplib test on the other Travis CI jobs.

https://travis-ci.org/python/cpython/jobs/637325027

Warning, treated as error:

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File "library/nntplib.rst", line ?, in default

Failed example:

    s = NNTP('news.gmane.io')

Exception raised:

    Traceback (most recent call last):

      File "/home/travis/build/python/cpython/Lib/doctest.py", line 1329, in __run

        exec(compile(example.source, filename, "single",

      File "<doctest default[0]>", line 1, in <module>

        s = NNTP('news.gmane.io')

      File "/home/travis/build/python/cpython/Lib/nntplib.py", line 1045, in __init__

        self.sock = self._create_socket(timeout)

      File "/home/travis/build/python/cpython/Lib/nntplib.py", line 1062, in _create_socket

        return socket.create_connection((self.host, self.port), timeout)

      File "/home/travis/build/python/cpython/Lib/socket.py", line 843, in create_connection

        raise err

      File "/home/travis/build/python/cpython/Lib/socket.py", line 831, in create_connection

        sock.connect(sa)

    ConnectionRefusedError: [Errno 111] Connection refused