Fix error message from KeyForObj when passing an invalid struct.

impl/memory/datastore_test.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.
 
 package memory
 
 import (
         "fmt"
         "testing"
         "time"
@@ skipping 127 matching lines @@
                                         So(testGetMeta(c, k), ShouldEqual, 22)
 
                                         So(ds.Put(&Foo{ID: 1}), ShouldBeNil)
                                         So(testGetMeta(c, k), ShouldEqual, 23)
                                 })
 
                                 Convey("can Get", func() {
                                         vals := make([]dsS.PropertyMap, len(keys))
                                         for i := range vals {
                                                 vals[i] = dsS.PropertyMap{}
-                                                So(vals[i].SetMeta("key", keys[i]), ShouldBeNil)
+                                                So(vals[i].SetMeta("key", keys[i]), ShouldBeTrue)
                                         }
                                         So(ds.GetMulti(vals), ShouldBeNil)
 
                                         for i, val := range vals {
                                                 So(val, ShouldResemble, dsS.PropertyMap{
                                                         "Val":  {dsS.MkProperty(10)},
                                                         "$key": {dsS.MkPropertyNI(keys[i])},
                                                 })
                                         }
                                 })
@@ skipping 77 matching lines @@
                                         }, nil)
                                         So(err, ShouldBeNil)
                                         So(ds.Get(&Foo{ID: 1}), ShouldEqual, dsS.ErrNoSuchEntity)
                                 })
 
                                 Convey("A Get counts against your group count", func() {
                                         err := ds.RunInTransaction(func(c context.Context) error {
                                                 ds := dsS.Get(c)
 
                                                 pm := dsS.PropertyMap{}
-                                                So(pm.SetMeta("key", ds.NewKey("Foo", "", 20, nil)), ShouldBeNil)
+                                                So(pm.SetMeta("key", ds.NewKey("Foo", "", 20, nil)), ShouldBeTrue)
                                                 So(ds.Get(pm), ShouldEqual, dsS.ErrNoSuchEntity)
 
-                                                So(pm.SetMeta("key", k), ShouldBeNil)
+                                                So(pm.SetMeta("key", k), ShouldBeTrue)
                                                 So(ds.Get(pm).Error(), ShouldContainSubstring, "cross-group")
                                                 return nil
                                         }, nil)
                                         So(err, ShouldBeNil)
                                 })
 
                                 Convey("Get takes a snapshot", func() {
                                         err := ds.RunInTransaction(func(c context.Context) error {
                                                 ds := dsS.Get(c)
 
@@ skipping 364 matching lines @@
                 So(ds.Put(&Model{ID: 1, Value: []int64{20, 30}}), ShouldBeNil)
 
                 vals := []dsS.PropertyMap{}
                 So(ds.GetAll(dsS.NewQuery("Model").Project("Value"), &vals), ShouldBeNil)
                 So(len(vals), ShouldEqual, 2)
 
                 So(vals[0]["Value"][0].Value(), ShouldEqual, 20)
                 So(vals[1]["Value"][0].Value(), ShouldEqual, 30)
         })
 }