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:

**********************************************************************

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

Same for news.gmane.org

>>> s = nntplib.NNTP('news.gmane.org')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/corona10/oss/cpython/Lib/nntplib.py", line 1045, in __init__
    self.sock = self._create_socket(timeout)
  File "/Users/corona10/oss/cpython/Lib/nntplib.py", line 1062, in _create_socket
    return socket.create_connection((self.host, self.port), timeout)
  File "/Users/corona10/oss/cpython/Lib/socket.py", line 843, in create_connection
    raise err
  File "/Users/corona10/oss/cpython/Lib/socket.py", line 831, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [Errno 61] Connection refused

s = nntplib.NNTP('nntp.perl.org')
s = nntplib.NNTP('news.mozilla.org')

I 've checked a few servers list to use.
But I don't know that they are proper to use.

But for now on, IMHO skip is better choice.

FYI, gmane.io is down for a server move today.  It should be back in service by 2100 GMT.

> FYI, gmane.io is down for a server move today.  It should be back in service by 2100 GMT.

I propose to do nothing and wait. Travis CI is not currently preventing to merge a PR.

I should have checked first.  The move was completed ahead of schedule and it's now back in service.  The tests should no loner fail.

https://lars.ingebrigtsen.no/2020/01/15/news-gmane-org-is-now-news-gmane-io/

It seems like the GMANE server has been fixed.

Reopening as this is happening again -- twice for me: https://github.com/python/cpython/pull/20329/checks?check_run_id=701405252#step:7:117

gmane was down for maybe a day early this week.  We should expect this to continue happening on and off, as it has for years (I use it daily).  I suggest that we run the test when we can and skip (or connect elsewhere) when we cannot.

try:
    s = NNTP('news.gmane.io')
except ConnectionRefusedError as e:
    self.skipTest(f'Gmane down: {e}')