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

common/errors/transient_test.go

-// Copyright 2015 The LUCI Authors. All rights reserved.
-// Use of this source code is governed under the Apache License, Version 2.0
-// that can be found in the LICENSE file.
-
-package errors
-
-import (
-        "errors"
-        "testing"
-
-        . "github.com/smartystreets/goconvey/convey"
-)
-
-func TestTransientError(t *testing.T) {
-        t.Parallel()
-
-        Convey(`A nil error`, t, func() {
-                err := error(nil)
-
-                Convey(`Is not transient.`, func() {
-                        So(IsTransient(err), ShouldBeFalse)
-                })
-
-                Convey(`Returns nil when wrapped with a transient error.`, func() {
-                        So(WrapTransient(err), ShouldBeNil)
-                })
-        })
-
-        Convey(`An error`, t, func() {
-                err := errors.New("test error")
-
-                Convey(`Is not transient.`, func() {
-                        So(IsTransient(err), ShouldBeFalse)
-                })
-                Convey(`When wrapped with a transient error`, func() {
-                        terr := WrapTransient(err)
-                        Convey(`Has the same error string.`, func() {
-                                So(terr.Error(), ShouldEqual, "test error")
-                        })
-                        Convey(`Is transient.`, func() {
-                                So(IsTransient(terr), ShouldBeTrue)
-                        })
-                })
-
-                Convey(`A MultiError with a transient sub-error is transient.`, func() {
-                        So(IsTransient(MultiError{nil, WrapTransient(err), err}), ShouldBeTrue)
-                })
-        })
-}