[alerts-dispatcher] switch to OptionalLogin

go/src/infra/monitoring/dispatcher/dispatcher.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Dispatcher usage:
 // go run infra/monitoring/dispatcher
 // Expects gatekeeper.json to be in the current directory.
 
 package main
 
@@ skipping 214 matching lines @@
         flag.Parse()
 
         authOptions := auth.Options{
                 ServiceAccountJSONPath: *serviceAccountJSON,
                 Scopes: []string{
                         auth.OAuthScopeEmail,
                         "https://www.googleapis.com/auth/projecthosting",
                 },
         }
 
-        mode := auth.SilentLogin
+        mode := auth.OptionalLogin
         if *login {
                 mode = auth.InteractiveLogin
         }
 
         transport, err := auth.NewAuthenticator(mode, authOptions).Transport()
         if err != nil {
                 log.Errorf("AuthenticatedTransport: %v", err)
                 if !*login {
                         log.Errorf("Consider re-running with -login")
                 }
@@ skipping 115 matching lines @@
         logging.Set(ctx, log)
         defer cancel()
 
         loopResults := looper.Run(ctx, f, cycle, *maxErrs, clock.GetSystemClock())
 
         if !loopResults.Success {
                 log.Errorf("Failed to run loop, %v errors", loopResults.Errs)
                 os.Exit(1)
         }
 }