more descriptive error message

lib/modules/http.js

@@ -443,16 +443,21 @@ module.exports.create = function (deps, conf, greenlockMiddleware) {
           });
         });
 
+
         prom.then(function (handled) {
+          // XXX TODO SECURITY html escape
+					var host = (headers.host || '[no host header]').replace(/</, '&lt;');
+					// TODO specify filepath of config file or database connection, etc
+          var msg = "Bad Gateway: Goldilocks accepted '" + host + "' but no module (neither static nor proxy) was designated to handle it. Check your config file.";
           if (!handled) {
             conn.end([
-              'HTTP/1.1 404 Not Found'
+              'HTTP/1.1 502 Bad Gateway'
             , 'Date: ' + (new Date()).toUTCString()
             , 'Content-Type: text/html'
-            , 'Content-Length: 9'
+            , 'Content-Length: ' + msg.length
             , 'Connection: close'
             , ''
-            , 'Not Found'
+            , msg
             ].join('\r\n'));
           }
         });