veyron.io/veyron/veyron/tools/build:  Convert to verror2.

The change updates veyron.io/veyron/veyron/tools/build/impl_test.go
to use verror2.

The import statement renames verror2 to verror so that when we finally remove
verror, and rename verror2 to verror, the change will be simple.

Change-Id: I35fdb6095c3dae0746fd5a9bea5760372da0d013
diff --git a/tools/build/impl_test.go b/tools/build/impl_test.go
index 4f4d3f7..59f832d 100644
--- a/tools/build/impl_test.go
+++ b/tools/build/impl_test.go
@@ -11,14 +11,12 @@
 	"veyron.io/veyron/veyron2/rt"
 	"veyron.io/veyron/veyron2/services/mgmt/binary"
 	"veyron.io/veyron/veyron2/services/mgmt/build"
-	"veyron.io/veyron/veyron2/verror"
+	verror "veyron.io/veyron/veyron2/verror2"
 	"veyron.io/veyron/veyron2/vlog"
 
 	"veyron.io/veyron/veyron/profiles"
 )
 
-var errInternalError = verror.Internalf("internal error")
-
 type mock struct{}
 
 func (mock) Build(ctx build.BuilderBuildContext, arch build.Architecture, opsys build.OperatingSystem) ([]byte, error) {
@@ -28,7 +26,7 @@
 	}
 	if err := iterator.Err(); err != nil {
 		vlog.Errorf("Advance() failed: %v", err)
-		return nil, errInternalError
+		return nil, verror.Make(verror.Internal, ctx)
 	}
 	return nil, nil
 }