Added global ajax error handler to show a flash notification for failed requests.

CHANGELOG

@@ -145,6 +145,7 @@ v 8.9.0 (unreleased)
   - Filter parameters for request_uri value on instrumented transactions.
   - Remove duplicated keys add UNIQUE index to keys fingerprint column
   - ExtractsPath get ref_names from repository cache, if not there access git.
+  - Show a flash warning about the error detail of XHR requests which failed with status code 404 and 500
   - Cache user todo counts from TodoService
   - Ensure Todos counters doesn't count Todos for projects pending delete
   - Add left/right arrows horizontal navigation

app/assets/javascripts/application.js.coffee

@@ -185,6 +185,15 @@ $ ->
       else
         buttons.enable()
 
+  $(document).ajaxError (e, xhrObj, xhrSetting, xhrErrorText) ->
+
+    if xhrObj.status is 401
+      new Flash 'You need to be logged in.', 'alert'
+
+    else if xhrObj.status in [ 404, 500 ]
+      new Flash 'Something went wrong on our end.', 'alert'
+
+
   # Show/Hide the profile menu when hovering the account box
   $('.account-box').hover -> $(@).toggleClass('hover')