Show a confirmation on asset delete. Fixes STUD-375.

cms/djangoapps/contentstore/features/upload.feature

@@ -21,6 +21,7 @@ Feature: Upload Files
         When I upload the file "test"
         And I delete the file "test"
         Then I should not see the file "test" was uploaded
+        And I see a confirmation that the file was deleted
 
     Scenario: Users can download files
         Given I have opened a new course in studio

cms/djangoapps/contentstore/features/upload.py

@@ -90,6 +90,12 @@ def modify_upload(_step, file_name):
         cur_file.write(new_text)
 
 
+@step('I see a confirmation that the file was deleted')
+def i_see_a_delete_confirmation(step):
+    alert_css = '#alert-confirmation'
+    assert world.is_css_present(alert_css)
+
+
 def get_index(file_name):
     names_css = 'td.name-col > a.filename'
     all_names = world.css_find(names_css)

cms/static/js/views/assets.js

@@ -23,7 +23,11 @@ function removeAsset(e){
                         { 'location': row.data('id') },
                         function() {
                             // show the post-commit confirmation
-                            $(".wrapper-alert-confirmation").addClass("is-shown").attr('aria-hidden','false');
+                            var deleted = new CMS.Views.Alert.Confirmation({
+                                title: gettext("Your file has been deleted."),
+                                closeIcon: false
+                            });
+                            deleted.show();
                             row.remove();
                             analytics.track('Deleted Asset', {
                                 'course': course_location_analytics,