Add infraenv, setup creds and tee for Kitchen.

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

Index: go/src/infra/libs/infraenv/creds.go
diff --git a/go/src/infra/libs/infraenv/creds.go b/go/src/infra/libs/infraenv/creds.go
new file mode 100644
index 0000000000000000000000000000000000000000..a60874ade20acbd33f9267ca8198dade99bf54ae
--- /dev/null
+++ b/go/src/infra/libs/infraenv/creds.go
@@ -0,0 +1,46 @@
+// 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
+}