sheriff_o_matic: Add error if ajax request fails.

appengine/sheriff_o_matic/ui/ct-failure-card-buttons.html

Index: appengine/sheriff_o_matic/ui/ct-failure-card-buttons.html
diff --git a/appengine/sheriff_o_matic/ui/ct-failure-card-buttons.html b/appengine/sheriff_o_matic/ui/ct-failure-card-buttons.html
index e9ac9028b6cd551d4c427a12bb9b9714e93f3690..87b3be3234ba4c864e69e6268d21d03d7fb13368 100644
--- a/appengine/sheriff_o_matic/ui/ct-failure-card-buttons.html
+++ b/appengine/sheriff_o_matic/ui/ct-failure-card-buttons.html
@@ -33,6 +33,7 @@ found in the LICENSE file.
         padding: 6px 22px;
       }
     </style>
+    <ct-user-prefs id="userPrefs"></ct-user-prefs>
     <a is="pushstate-anchor" href="{{ group.examineUrl }}" id="examineLink">Examine</a>
     <template if="{{ !group.isSnoozed }}">
       <ct-button id="snooze" on-tap="{{ snooze }}" label="Snooze"></ct-button>
@@ -57,12 +58,32 @@ found in the LICENSE file.
       <ct-button on-tap="{{ removeBug }}" dismissive role="button" id="dialogRemoveBug" label="Remove bug link"></ct-button>
       <ct-button on-tap="{{ saveBug }}" affirmative role="button" id="dialogOk" label="OK"></ct-button>
     </paper-action-dialog>
+    <paper-action-dialog heading="Error" transition="paper-transition-center" id="loginDialog">
+      <div id="accessDeniedMessage">
+        Please <a href="{{ $.userPrefs.values.loginUrl }}">log in</a> to modify alerts.
+      </div>
+      <div id="otherMessage"></div>
+    </paper-action-dialog>
   </template>
   <script>
     Polymer({
       group: null,
       _fileBugClicked: false,
 
+      ready: function() {
+        this.group.errorCallback = this.errorCallback.bind(this);
+      },
+
+      errorCallback: function(args) {
+        if (args.message == "Forbidden") {
+          this.$.otherMessage.hidden = true;
+        } else {
+          this.$.accessDeniedMessage.hidden = true;
+          this.$.otherMessage.textContent = args.message;
+        }
+        this.$.loginDialog.open();
+      },
+
       snooze: function() {
         this.group.snoozeUntil(Date.now() + 60 * 60 * 1000);
         ga('send', 'event', 'snooze', 'click');