allow notebook tour instantiation to fail

can fail with SecurityError,
depending on browser privacy settings

disable UI Tour menu entry if tour instantiation fails

ref: sorich87/bootstrap-tour#262

IPython/html/static/notebook/js/main.js

@@ -57,7 +57,11 b' function (marked) {'
     IPython.layout_manager = new IPython.LayoutManager();
     IPython.pager = new IPython.Pager('div#pager', 'div#pager_splitter');
     IPython.quick_help = new IPython.QuickHelp();
-    IPython.tour = new IPython.NotebookTour();
+    try {
+        IPython.tour = new IPython.NotebookTour();
+    } catch (e) {
+        console.log("Failed to instantiate Notebook Tour", e);
+    }
     IPython.login_widget = new IPython.LoginWidget('span#login_widget', opts);
     IPython.notebook = new IPython.Notebook('div#notebook', opts);
     IPython.keyboard_manager = new IPython.KeyboardManager();

IPython/html/static/notebook/js/menubar.js

@@ -280,9 +280,13 b' var IPython = (function (IPython) {'
             IPython.notebook.restart_kernel();
         });
         // Help
-        this.element.find('#notebook_tour').click(function () {
-            IPython.tour.start();
-        });
+        if (IPython.tour) {
+            this.element.find('#notebook_tour').click(function () {
+                IPython.tour.start();
+            });
+        } else {
+            this.element.find('#notebook_tour').addClass("disabled");
+        }
         this.element.find('#keyboard_shortcuts').click(function () {
             IPython.quick_help.show_keyboard_shortcuts();
         });