Refactor a bit.

service/memcache/errors.go

Index: service/memcache/errors.go
diff --git a/service/memcache/errors.go b/service/memcache/errors.go
new file mode 100644
index 0000000000000000000000000000000000000000..d102f4252573d769aa9a3d90e5f6a2ea74e72389
--- /dev/null
+++ b/service/memcache/errors.go
@@ -0,0 +1,23 @@
+// 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.
+
+// This file contains errors which are mirrors/duplicates of the
+// upstream SDK errors. This exists so that users can depend solely on this
+// wrapper library without also needing to import the SDK.
+
+package memcache
+
+import (
+	orig "google.golang.org/appengine/memcache"
+)
+
+// These are pass-through versions from the managed-VM SDK. All implementations
+// must return these (exact) errors (not just an error with the same text).
+var (
+	ErrCacheMiss   = orig.ErrCacheMiss
+	ErrCASConflict = orig.ErrCASConflict
+	ErrNoStats     = orig.ErrNoStats
+	ErrNotStored   = orig.ErrNotStored
+	ErrServerError = orig.ErrServerError
+)