Skip the test not if it is OSX, but if it is Py3.6+, which appears to be the origination of the behavior breakage

Author: Jordan Adler

src/future/utils/__init__.py

@@ -57,6 +57,7 @@
 
 PY3 = sys.version_info[0] == 3
 PY35_PLUS = sys.version_info[0:2] >= (3, 5)
+PY36_PLUS = sys.version_info[0:2] >= (3, 6)
 PY2 = sys.version_info[0] == 2
 PY26 = sys.version_info[0:2] == (2, 6)
 PY27 = sys.version_info[0:2] == (2, 7)

tests/test_future/test_urllibnet.py

@@ -109,9 +109,8 @@ def test_getcode(self):
 
     # On Windows, socket handles are not file descriptors; this
     # test can't pass on Windows.
-    #
-    # On macOS, this behavior is undocumented and this test fails.
-    @unittest.skipIf(sys.platform in ('darwin', 'win32',), 'not appropriate for macOS or Windows')
+    @unittest.skipIf(sys.platform in ('darwin', 'win32',), 'not appropriate for Windows')
+    @unittest.skipIf(utils.PY36_PLUS, 'test not applicable on Python 3.5 and higher')
     @skip26
     def test_fileno(self):
         # Make sure fd returned by fileno is valid.