Change user events tutorial Redis error to be an inline box

Fixes #1653

endpoints/realtime.py

@@ -99,6 +99,8 @@ def user_test():
 @require_session_login
 def user_subscribe():
   def wrapper(listener):
+    yield 'data: %s\n\n' % json.dumps({})
+
     for event_id, data in listener.event_stream():
       message = {'event': event_id, 'data': data}
       json_string = json.dumps(message)

static/directives/angular-tour-ui.html

@@ -5,6 +5,11 @@
     Your browser does not support features required for this tour. Please upgrade and try again.
   </div>
 
+  <div class="co-alert co-alert-warning" ng-show="step.signal.$hasError">
+    There was an error registering to listen for server side events. Steps of the tutorial may not be
+    possible. If this problem persists, please contact support.
+  </div>
+
   <div class="tour-contents" ng-show="supported">
     <div class="step-title" ng-shpw="step.title">{{ step.title }}</div>
     <div class="slide-animate-container">

static/js/tour.js

@@ -284,11 +284,20 @@ angular.module("angular-tour", [])
         var fullUrl = tourScope._replaceData(url);
         checker.$source = new EventSource(fullUrl);
         checker.$source.onmessage = function(e) {
-          checker.$message = JSON.parse(e.data);
+          var parsed = JSON.parse(e.data);
+          if (!parsed['data']) {
+            return;
+          }
+
+          checker.$message = parsed;
         };
+
+        checker.$source.onopen = function(e) {
+          checker.$hasError = false;
+        };
+
         checker.$source.onerror = function(e) {
-          bootbox.alert('Could not read user events from server due to a Redis issue. ' +
-                        ' Please contact support.')
+          checker.$hasError = true;
         };
       };