[FIX] pos_lot_selection: ES6 code breaks phantomjs tests

Object.assign is introduced in ES6 (2015) which is not supported by
PhantomJS. Replace it with the equivalent _.extend function to prevent
frontend tests from failing.

1. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign#Specifications
2. ariya/phantomjs#14506

pos_lot_selection/README.rst

@@ -62,6 +62,7 @@ Contributors
 * David <[email protected]>
   * (https://www.tecnativa.com)
 * Ignacio Ales <[email protected]>
+* Kiril Vangelovski <[email protected]>
 
 Do not contact contributors directly about support or help with technical issues.
 

pos_lot_selection/static/src/js/chrome.js

@@ -1,4 +1,5 @@
 /* Copyright 2018 Tecnativa - David Vidal
+   Copyright 2019 Lambda IS DOOEL <https://www.lambda-is.com>
    License LGPL-3.0 or later (https://www.gnu.org/licenses/lgpl). */
 
 odoo.define("pos_lot_selection.chrome", function (require) {
@@ -14,7 +15,7 @@ odoo.define("pos_lot_selection.chrome", function (require) {
             var events = {
                 "change .packlot-line-select": "lot_to_input",
             };
-            packlotline.events = Object.assign(
+            packlotline.events = _.extend(
                 packlotline.events, events
             );
             // Add methods over instanced popup