Clean new Flash() and stop disabling no-new (eslint) when possible

app/assets/javascripts/boards/components/board_sidebar.js

@@ -2,6 +2,7 @@
 
 import Vue from 'vue';
 import Flash from '../../flash';
+import { __ } from '../../locale';
 import Sidebar from '../../right_sidebar';
 import eventHub from '../../sidebar/event_hub';
 import assigneeTitle from '../../sidebar/components/assignees/assignee_title';
@@ -95,7 +96,7 @@ gl.issueBoards.BoardSidebar = Vue.extend({
         })
         .catch(() => {
           this.loadingAssignees = false;
-          return new Flash('An error occurred while saving assignees');
+          Flash(__('An error occurred while saving assignees'));
         });
     },
   },

app/assets/javascripts/boards/components/modal/footer.js

-/* eslint-disable no-new */
-
 import Vue from 'vue';
 import Flash from '../../../flash';
+import { __ } from '../../../locale';
 import './lists_dropdown';
 import { pluralize } from '../../../lib/utils/text_utility';
 
@@ -36,7 +35,7 @@ gl.issueBoards.ModalFooter = Vue.extend({
       gl.boardService.bulkUpdate(issueIds, {
         add_label_ids: [list.label.id],
       }).catch(() => {
-        new Flash('Failed to update issues, please try again.', 'alert');
+        Flash(__('Failed to update issues, please try again.'));
 
         selectedIssues.forEach((issue) => {
           list.removeIssue(issue);

app/assets/javascripts/boards/components/sidebar/remove_issue.js

-/* eslint-disable no-new */
-
 import Vue from 'vue';
 import Flash from '../../../flash';
+import { __ } from '../../../locale';
 
 const Store = gl.issueBoards.BoardsStore;
 
@@ -45,7 +44,7 @@ gl.issueBoards.RemoveIssueBtn = Vue.extend({
         },
       };
       Vue.http.patch(this.updateUrl, data).catch(() => {
-        new Flash('Failed to remove issue from board, please try again.', 'alert');
+        Flash(__('Failed to remove issue from board, please try again.'));
 
         lists.forEach((list) => {
           list.addIssue(issue);