config_service: change error message for error 403.

appengine/config_service/ui/src/config-ui/config-set.html

 <!--
   Copyright 2017 The LUCI Authors. All rights reserved.
   Use of this source code is governed under the Apache License, Version 2.0
   that can be found in the LICENSE file.
 -->
 
 <link rel="import" href="config-file-card.html">
 <link rel="import" href="../../bower_components/iron-ajax/iron-ajax.html">
 <link rel="import" href="../../bower_components/iron-icons/iron-icons.html">
 <link rel="import" href="../../bower_components/paper-item/paper-item.html">
@@ skipping 256 matching lines @@
       _onRefreshError: function() {
         this.isRefreshing = false;
         this.refreshMessage = "Error: Files could not be refreshed.";
         this.fire('refreshError');
       },
 
       _onRequestError: function(event) {
         var error = parseInt(event.detail.error.message.match(/\d+/g));
         this.isLoading = false;
         if (error === 403) {
-          this.errorMessage = "Authorization required to view this config set. " +
-              "Please sign in.";
+          this.errorMessage = "Access denied. If you are not signed in, please do so. " +
+              "Otherwise, try again later.";

[Sergey Berezin, 2017/07/26 18:46:42]

"Access denied" is probably the only thing that we can say at this point. Trying
again later will likely not work, the user needs to gain access first.

Can we detect whether the user is signed in or not from Polymer? (maybe query
the auth element?)
Ideally, the message would change depending on whether the user is actually
logged in or not, e.g. "Access denied, please sign in." vs. "Access denied,
<username> is not authorized to access this config set. Request access or sign
in as a different user."

If detecting sign-in is nontrivial, I'd just leave it with "Access denied.".

         } else if (500 <= error && error < 600) {
           this.errorMessage = "Internal server error.";
         } else {
           this.errorMessage = "Error occured. Try again later.";
         }
         this.fire('fetchError');
       }
 
     });
   </script>
 </dom-module>