Better handling of proxy requests errors.

src/proxy-request.js

@@ -81,8 +81,6 @@ function proxyRequest(opts, upReq, upRes) {
 	var request = isSecure ? httpsRequest : httpRequest;
 
 	var downReq = request(opts, function onResponse(downRes) {
-		debug('response received');
-
 		forEach(downRes.headers, function forwardResponseHeaderUp(value, name) {
 			upRes.setHeader(name, value);
 		});

src/xo.coffee

@@ -443,11 +443,20 @@ class $XO extends $EventEmitter
 
     $proxyRequest request, req, res
 
-    handleError = (error) ->
-      console.warn error.stack ? error
+    closeConnection = ->
+      unless res.headersSent
+        res.writeHead 500
+      res.end()
+      return
+
+    req.on 'error', (error) ->
+      console.warn 'request error', error.stack ? error
+      closeConnection()
+      return
+    res.on 'error', (error) ->
+      console.warn 'response error', error.stack ? error
+      closeConnection()
       return
-    req.on 'error', handleError
-    res.on 'error', handleError
 
     return