Add infraenv, setup creds and tee for Kitchen.

go/src/infra/libs/infraenv/creds.go

+// Copyright 2016 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.
+
+package infraenv
+
+import (
+        "os"
+        "path/filepath"
+
+        "github.com/luci/luci-go/common/errors"
+        "google.golang.org/cloud/compute/metadata"
+)
+
+// ErrNotFound is returned if the requested credential is not found.
+var ErrNotFound = errors.New("not found")
+
+// OnGCE will return true if the current system is a Google Compute Engine
+// system.
+var OnGCE = metadata.OnGCE
+
+// GetLogDogServiceAccountJSON scans the credential directories for the LogDog
+// service account JSON file.
+//
+// If the credential could not be located on this system, ErrNotFound will be
+// returned.
+func GetLogDogServiceAccountJSON() (string, error) {
+        return findCredentialFile(systemCredentialDirs, "service-account-luci-logdog-publisher.json")
+}
+
+func findCredentialFile(dirs []string, name string) (string, error) {
+        for _, d := range dirs {
+                candidate := filepath.Join(d, name)
+                if _, err := os.Stat(candidate); err != nil {
+                        if os.IsNotExist(err) {
+                                continue
+                        }
+
+                        return "", errors.Annotate(err).Reason("failed to check [%(path)s]").D("path", candidate).Err()
+                }
+
+                return candidate, nil
+        }
+
+        return "", ErrNotFound
+}