Handle sign out failure

h/static/scripts/auth/auth.coffee

@@ -22,9 +22,11 @@ configure = [
     ]
 
     identityProvider.forgetAuthentication = [
-      'session',
-      (session) ->
-        session.logout({}).$promise
+      'flash', 'session',
+      (flash,   session) ->
+        session.logout({}).$promise.catch (err) ->
+          flash 'error', 'Sign out failed!'
+          throw err
     ]
 
     identityProvider.requestAuthentication = [

h/static/scripts/identity.coffee

@@ -66,7 +66,7 @@ identityProvider = ->
       ###
       logout: ->
         result = $injector.invoke(provider.forgetAuthentication, provider)
-        $q.when(result).finally(onlogout)
+        $q.when(result).then(onlogout)
 
       ###*
       # @ngdoc method