added the error handling to avoid http-party/node-http-proxy#527

Author: Tomoya32

src/server.js

@@ -29,6 +29,18 @@ app.use('/api', (req, res) => {
   proxy.web(req, res);
 });
 
+// added the error handling to avoid https://github.com/nodejitsu/node-http-proxy/issues/527
+proxy.on('error', (error, req, res) => {
+  let json;
+  console.log('proxy error', error);
+  if (!res.headersSent) {
+    res.writeHead(500, {'content-type': 'application/json'});
+  }
+
+  json = { error: 'proxy_error', reason: error.message };
+  res.end(JSON.stringify(json));
+});
+
 app.use((req, res) => {
   if (__DEVELOPMENT__) {
     // Do not cache webpack stats: the script file would change since