Issue #12326: refactor usage of sys.platform

 * Use str.startswith(tuple): I didn't know this Python feature, Python rocks!
 * Replace sometimes sys.platform.startswith('linux') with
   sys.platform == 'linux'
 * sys.platform doesn't contain the major version on Cygwin on Mac OS X
   (it's just 'cygwin' and 'darwin')
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index 35beae4..556bbba 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.startswith('linux') or sys.platform == 'darwin':
+        if sys.platform in ('linux', 'darwin'):
             for existing in (True, False):
                 fd, fn = tempfile.mkstemp()
                 os.close(fd)