[errors] de-specialize Transient in favor of Tags.

server/auth/auth_test.go

Index: server/auth/auth_test.go
diff --git a/server/auth/auth_test.go b/server/auth/auth_test.go
index 493edc75e137b89865ddf083ea6876ee771bb2f4..f195c175fdf7b72f90a724ea698de535af353bf1 100644
--- a/server/auth/auth_test.go
+++ b/server/auth/auth_test.go
@@ -21,6 +21,7 @@ import (
 	"github.com/luci/luci-go/server/auth/signing"
 
 	"github.com/luci/luci-go/common/errors"
+	"github.com/luci/luci-go/common/retry/transient"
 	. "github.com/luci/luci-go/common/testing/assertions"
 	. "github.com/smartystreets/goconvey/convey"
 )
@@ -176,7 +177,7 @@ func TestMiddleware(t *testing.T) {
 
 	Convey("Transient error", t, func() {
 		rr := call(&Authenticator{
-			Methods: []Method{fakeAuthMethod{err: errors.WrapTransient(errors.New("boo"))}},
+			Methods: []Method{fakeAuthMethod{err: errors.New("boo", transient.Tag)}},
 		})
 		So(rr.Code, ShouldEqual, 500)
 		So(rr.Body.String(), ShouldEqual, "Transient error during authentication\n")