errors working with babel 6, export v3 shared modules in main common module

common/script/api-v3/errors.js

@@ -1,6 +1,8 @@
+import extendableBuiltin from './libs/extendableBuiltin';
+
 // Base class for custom application errors
 // It extends Error and capture the stack trace
-export class CustomError extends Error {
+export class CustomError extends extendableBuiltin(Error) {
   constructor () {
     super();
     Error.captureStackTrace(this, this.constructor);

common/script/api-v3/libs/extendableBuiltin.js

@@ -0,0 +1,11 @@
+// Babel 6 doesn't support extending native class (Error, Array, ...)
+// This function makes it possible to extend native classes with the same results as Babel 5
+module.exports = function extendableBuiltin (klass) {
+  function ExtendableBuiltin () {
+    klass.apply(this, arguments);
+  }
+  ExtendableBuiltin.prototype = Object.create(klass.prototype);
+  Object.setPrototypeOf(ExtendableBuiltin, klass);
+
+  return ExtendableBuiltin;
+};

common/script/api-v3/scoreTask.js

@@ -1,7 +1,7 @@
 import _ from 'lodash';
 import {
   NotAuthorized,
-} from '../../../website/src/libs/api-v3/errors';
+} from './errors';
 import i18n from '../i18n';
 
 const MAX_TASK_VALUE = 21.27;