[errors] Greatly simplify common/errors package.

dm/tools/dmtool/vizQuery.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 main
 
 import (
         "bytes"
         "fmt"
         "os"
@@ skipping 216 matching lines @@
         }
         client.Options.Insecure = lhttp.IsLocalHost(r.host)
         dc := dm.NewDepsPRPCClient(client)
 
         prev := ""
         seq := 0
 
         for c.Err() == nil {
                 gdata, err := runQuery(c, dc, query)
                 if err != nil {
-                        if errors.Contains(err, context.Canceled) {
+                        if errors.Any(err, func(err error) bool { return err == context.Canceled }) {
                                 return 0
                         }
                         logging.WithError(err).Errorf(c, "error running query")
                         return 1
                 }
 
                 if gdata != nil {
                         newVal := renderDotFile(gdata)
                         if prev != newVal {
                                 prev = newVal
@@ skipping 28 matching lines @@
                                                 return 0
                                         }
                                 }
                         }
                 }
 
                 clock.Sleep(c, time.Second/4)
         }
         return 0
 }