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

grpc/prpc/client_test.go

 // Copyright 2016 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 prpc
 
 import (
         "fmt"
         "io/ioutil"
         "net/http"
@@ skipping 193 matching lines @@
                                 }
 
                                 client.Options.PerRPCTimeout = 10 * time.Second
                                 client.Options.Retry = func() retry.Iterator {
                                         return &countingRetryIterator{
                                                 retries: &retries,
                                         }
                                 }
 
                                 err := client.Call(ctx, "prpc.Greeter", "SayHello", req, res)
-                                So(err.Error(), ShouldContainSubstring, "failed to send request")
+                                So(err.Error(), ShouldEqual, context.DeadlineExceeded.Error())
                                 So(retries, ShouldEqual, 0)
                         })
 
                         Convey(`With a maximum content length smaller than the response, returns "ErrResponseTooBig".`, func(c C) {
                                 client, server := setUp(sayHello(c))
                                 defer server.Close()
 
                                 client.MaxContentLength = 8
                                 err := client.Call(ctx, "prpc.Greeter", "SayHello", req, res)
                                 So(err, ShouldEqual, ErrResponseTooBig)
@@ skipping 108 matching lines @@
         retries *int
 }
 
 func (it *countingRetryIterator) Next(c context.Context, err error) time.Duration {
         *(it.retries)--
         if *it.retries <= 0 {
                 return retry.Stop
         }
         return 0
 }