bpo-38907: Suppress any exception when attempting to set V6ONLY.

[jaraco]

Fixes error attempting to bind to IPv4 address, identified after GH-17851.

https://bugs.python.org/issue38907

Automerge-Triggered-By: @jaraco

[miss-islington]

Thanks @jaraco for the PR 🌮🎉.. I'm working now to backport this PR to: 3.8.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[bedevere-bot]

GH-17865 is a backport of this pull request to the 3.8 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot x86 Windows7 3.8 has failed when building commit 33cb4a6.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/223/builds/59) and take a look at the build logs.
4. Check if the failure is related to this commit (33cb4a6) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/223/builds/59

Failed tests:

• test_compileall

Failed subtests:

• test_no_args_respects_force_flag - test.test_compileall.CommmandLineTestsNoSourceEpoch

Summary of the results of the build (if available):

== Tests result: FAILURE then ENV CHANGED ==

392 tests OK.

10 slowest tests:

• test_multiprocessing_spawn: 18 min 40 sec
• test_zipfile: 10 min 39 sec
• test_concurrent_futures: 8 min 28 sec
• test_regrtest: 5 min 10 sec
• test_venv: 4 min 17 sec
• test_lzma: 4 min 3 sec
• test_tarfile: 4 min 2 sec
• test_asyncio: 3 min 33 sec
• test_pickle: 2 min 55 sec
• test_embed: 2 min 30 sec

1 test altered the execution environment:
test_multiprocessing_spawn

30 tests skipped:
test_curses test_dbm_gnu test_dbm_ndbm test_devpoll test_epoll
test_fcntl test_fork1 test_gdb test_grp test_ioctl test_kqueue
test_multiprocessing_fork test_multiprocessing_forkserver test_nis
test_openpty test_ossaudiodev test_pipes test_poll test_posix
test_pty test_pwd test_readline test_resource test_spwd
test_syslog test_threadsignals test_wait3 test_wait4
test_xxtestfuzz test_zipfile64

1 re-run test:
test_compileall

Total duration: 1 hour 21 min

Click to see traceback logs

Traceback (most recent call last):
  File "D:\cygwin\home\db3l\buildarea\3.8.bolen-windows7\build\lib\test\test_py_compile.py", line 20, in wrapper
    return fxn(*args, **kwargs)
  File "D:\cygwin\home\db3l\buildarea\3.8.bolen-windows7\build\lib\test\test_py_compile.py", line 20, in wrapper
    return fxn(*args, **kwargs)
  File "D:\cygwin\home\db3l\buildarea\3.8.bolen-windows7\build\lib\test\test_compileall.py", line 322, in test_no_args_respects_force_flag
    self.assertRunOK('-f', PYTHONPATH=self.directory)
  File "D:\cygwin\home\db3l\buildarea\3.8.bolen-windows7\build\lib\test\test_compileall.py", line 271, in assertRunOK
    rc, out, err = script_helper.assert_python_ok(
  File "D:\cygwin\home\db3l\buildarea\3.8.bolen-windows7\build\lib\test\support\script_helper.py", line 157, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
  File "D:\cygwin\home\db3l\buildarea\3.8.bolen-windows7\build\lib\test\support\script_helper.py", line 143, in _assert_python
    res.fail(cmd_line)
  File "D:\cygwin\home\db3l\buildarea\3.8.bolen-windows7\build\lib\test\support\script_helper.py", line 70, in fail
    raise AssertionError("Process return code is %d\n"
AssertionError: Process return code is 1
command line: ['D:\\cygwin\\home\\db3l\\buildarea\\3.8.bolen-windows7\\build\\PCbuild\\win32\\python_d.exe', '-X', 'faulthandler', '-S', '-m', 'compileall', '-f']