TNL-3258 Reset group configuration model when a child content group is deleted…

TNL-3258 Reset group configuration model when a child content group is deleted (+5 squashed commits)
Squashed commits:
[450761c] found an alternative way to restore model when any of the nested model is deleted
[1b7eb85] passed the context to the inner functions
[c87dafd] refactored the model access using encapsulation instead of directly accessing it
[5d025ff] return the promise
[d8d1f50] fixup! quality (+1 squashed commit)
Squashed commits:
[daa7f81] reset the configuration when the model is deleted (+1 squashed commit)
Squashed commits:
[c7f41f7] reverted: skip test_can_delete_unused_content_group due to flakiness

cms/static/js/models/group_configuration.js

@@ -36,8 +36,11 @@ function(Backbone, _, str, gettext, GroupModel, GroupCollection) {
         }],
 
         initialize: function(attributes, options) {
+            this.on('remove:groups', this.groupRemoved);
+
             this.canBeEmpty = options && options.canBeEmpty;
             this.setOriginalAttributes();
+
             return this;
         },
 
@@ -120,6 +123,10 @@ function(Backbone, _, str, gettext, GroupModel, GroupCollection) {
                     };
                 }
             }
+        },
+
+        groupRemoved: function () {
+            this.setOriginalAttributes();
         }
     });
 

common/test/acceptance/tests/studio/test_studio_settings.py

@@ -4,7 +4,6 @@ Acceptance tests for Studio's Setting pages
 """
 from __future__ import unicode_literals
 from nose.plugins.attrib import attr
-from unittest import skip
 
 from base_studio_test import StudioCourseTest
 from bok_choy.promise import EmptyPromise
@@ -152,7 +151,6 @@ class ContentGroupConfigurationTest(StudioCourseTest):
         config = self.group_configurations_page.content_groups[0]
         self.assertTrue(config.delete_button_is_disabled)
 
-    @skip("TNL-3258")
     def test_can_delete_unused_content_group(self):
         """
         Scenario: Ensure that the user can delete unused content group.