Issue #12326: don't test the major version of sys.platform

Use startswith, instead of ==, when testing sys.platform to support
new platforms like Linux 3 or OpenBSD 5.
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index 793d29b..35beae4 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -527,7 +527,7 @@
     def test_builtin_handlers(self):
         # We can't actually *use* too many handlers in the tests,
         # but we can try instantiating them with various options
-        if sys.platform in ('linux2', 'darwin'):
+        if sys.platform.startswith('linux') or sys.platform == 'darwin':
             for existing in (True, False):
                 fd, fn = tempfile.mkstemp()
                 os.close(fd)