Produce a better error in case of malformed JSON
$ curl localhost:8777 -X POST -i -d '{"action": "version", "version": 6},' && echo ␄
HTTP/1.1 200 OK
Content-Type: text/json
Access-Control-Allow-Origin: http://localhost
Access-Control-Allow-Headers: *
Content-Length: 67
{"result": null, "error": "Extra data: line 1 column 36 (char 35)"}␄
$ curl localhost:8777 -X POST -i -d '{"action": "version", "version": 6},' -H "Origin: foo" && echo ␄
HTTP/1.1 403 Forbidden
Access-Control-Allow-Origin: http://localhost
Access-Control-Allow-Headers: *
␄
bffbb051f2