The code in _scproxy (a mac specific helper module to
detect proxy settings) had the wrong logic for detecting
if the checkbox 'Exclude simple hostnames' is checked. This
checkin fixes that.

As a result the test failure 'Issue8455' goes away on systems
where the checkbox is not checked.

I'm carefully avoiding saying that is fixes that issue,
test_urllib2_localnet assumes that system proxy settings are
empty (not just on OSX, see Issue8455 for details).
diff --git a/Mac/Modules/_scproxy.c b/Mac/Modules/_scproxy.c
index dd5a293..b393fd1 100644
--- a/Mac/Modules/_scproxy.c
+++ b/Mac/Modules/_scproxy.c
@@ -68,7 +68,7 @@
         aNum = CFDictionaryGetValue(proxyDict,
             kSCPropNetProxiesExcludeSimpleHostnames);
         if (aNum == NULL) {
-            v = PyBool_FromLong(1);
+            v = PyBool_FromLong(0);
         } else {
             v = PyBool_FromLong(cfnum_to_int32(aNum));
         }