Be slightly more verbose for #992

yesod-bin/Devel.hs

@@ -191,7 +191,10 @@ reverseProxy opts iappPort = do
     putStrLn $ "If you wish to test https capabilities, you should set the following variable:"
     putStrLn $ "  export APPROOT=https://127.0.0.1:" ++ show (develTlsPort opts)
     putStrLn ""
-    loop (race_ httpProxy httpsProxy) `Ex.onException` exitFailure
+    loop (race_ httpProxy httpsProxy) `Ex.catch` \e -> do
+        print (e :: Ex.SomeException)
+        exitFailure
+        Ex.throwIO e -- heh, just for good measure
   where
     loop proxies = forever $ do
         void proxies