======================================================================FAIL: test_imap4_host_default_value (test.test_imaplib.TestImaplib)----------------------------------------------------------------------Traceback (most recent call last):  File "/home/python/Lib/test/test_imaplib.py", line 94, in test_imap4_host_default_value    self.assertIn(cm.exception.errno, expected_errnos)AssertionError: 101 not found in [111, 99]----------------------------------------------------------------------I guess `errno.ENETUNREACH` should be added to the `expected_errnos` as it done within `test_create_connection` (test.test_socket.NetworkConnectionNoServer).

Did you see this failure somewhere in CI or is it in local machine? The imaplib test has below comment : if hasattr(errno, 'EADDRNOTAVAIL'):    # socket.create_connection() fails randomly with    # EADDRNOTAVAIL on Travis CI.    expected_errnos.append(errno.EADDRNOTAVAIL)As noted in initial report test_socket has ENETUNREACH addedhttps://github.com/python/cpython/blob/929b70473829f04dedb8e802abcbd506926886e1/Lib/test/test_socket.py#L4808 so ENETUNREACH could also be added to this test too?

I see this error on my local Bamboo CI (runs on CentOS 7).

New changeset3c7931e514faf509a39c218c2c9f55efb434628f by Victor Stinner in branch 'master':bpo-36629: Add support.get_socket_conn_refused_errs() (GH-12834)https://github.com/python/cpython/commit/3c7931e514faf509a39c218c2c9f55efb434628f

New changeset28ed39e83e4c545fa1da89fd7691cace280296f7 by Victor Stinner (Miss Islington (bot)) in branch '3.7':bpo-36629: Add support.get_socket_conn_refused_errs() (GH-12834) (GH-12835)https://github.com/python/cpython/commit/28ed39e83e4c545fa1da89fd7691cace280296f7

Thanks for your bug report Marat Sharafutdinov, it's now fixed in 3.7 and master (Python 2.7 is not affected, it doesn't have the test_imaplib test method).

Thank you for the patch, Victor!