diff --git a/vendor/google.golang.org/appengine/internal/internal.go b/vendor/google.golang.org/appengine/internal/internal.go
new file mode 100644
index 0000000..051ea39
--- /dev/null
+++ b/vendor/google.golang.org/appengine/internal/internal.go
@@ -0,0 +1,110 @@
+// Copyright 2011 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+// Package internal provides support for package appengine.
+//
+// Programs should not use this package directly. Its API is not stable.
+// Use packages appengine and appengine/* instead.
+package internal
+
+import (
+	"fmt"
+
+	"github.com/golang/protobuf/proto"
+
+	remotepb "google.golang.org/appengine/internal/remote_api"
+)
+
+// errorCodeMaps is a map of service name to the error code map for the service.
+var errorCodeMaps = make(map[string]map[int32]string)
+
+// RegisterErrorCodeMap is called from API implementations to register their
+// error code map. This should only be called from init functions.
+func RegisterErrorCodeMap(service string, m map[int32]string) {
+	errorCodeMaps[service] = m
+}
+
+type timeoutCodeKey struct {
+	service string
+	code    int32
+}
+
+// timeoutCodes is the set of service+code pairs that represent timeouts.
+var timeoutCodes = make(map[timeoutCodeKey]bool)
+
+func RegisterTimeoutErrorCode(service string, code int32) {
+	timeoutCodes[timeoutCodeKey{service, code}] = true
+}
+
+// APIError is the type returned by appengine.Context's Call method
+// when an API call fails in an API-specific way. This may be, for instance,
+// a taskqueue API call failing with TaskQueueServiceError::UNKNOWN_QUEUE.
+type APIError struct {
+	Service string
+	Detail  string
+	Code    int32 // API-specific error code
+}
+
+func (e *APIError) Error() string {
+	if e.Code == 0 {
+		if e.Detail == "" {
+			return "APIError <empty>"
+		}
+		return e.Detail
+	}
+	s := fmt.Sprintf("API error %d", e.Code)
+	if m, ok := errorCodeMaps[e.Service]; ok {
+		s += " (" + e.Service + ": " + m[e.Code] + ")"
+	} else {
+		// Shouldn't happen, but provide a bit more detail if it does.
+		s = e.Service + " " + s
+	}
+	if e.Detail != "" {
+		s += ": " + e.Detail
+	}
+	return s
+}
+
+func (e *APIError) IsTimeout() bool {
+	return timeoutCodes[timeoutCodeKey{e.Service, e.Code}]
+}
+
+// CallError is the type returned by appengine.Context's Call method when an
+// API call fails in a generic way, such as RpcError::CAPABILITY_DISABLED.
+type CallError struct {
+	Detail string
+	Code   int32
+	// TODO: Remove this if we get a distinguishable error code.
+	Timeout bool
+}
+
+func (e *CallError) Error() string {
+	var msg string
+	switch remotepb.RpcError_ErrorCode(e.Code) {
+	case remotepb.RpcError_UNKNOWN:
+		return e.Detail
+	case remotepb.RpcError_OVER_QUOTA:
+		msg = "Over quota"
+	case remotepb.RpcError_CAPABILITY_DISABLED:
+		msg = "Capability disabled"
+	case remotepb.RpcError_CANCELLED:
+		msg = "Canceled"
+	default:
+		msg = fmt.Sprintf("Call error %d", e.Code)
+	}
+	s := msg + ": " + e.Detail
+	if e.Timeout {
+		s += " (timeout)"
+	}
+	return s
+}
+
+func (e *CallError) IsTimeout() bool {
+	return e.Timeout
+}
+
+// NamespaceMods is a map from API service to a function that will mutate an RPC request to attach a namespace.
+// The function should be prepared to be called on the same message more than once; it should only modify the
+// RPC request the first time.
+var NamespaceMods = make(map[string]func(m proto.Message, namespace string))