[errors] Greatly simplify common/errors package.

vpython/application/subcommand_verify.go

 // Copyright 2017 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 application
 
 import (
         "strings"
 
         "github.com/maruel/subcommands"
@@ skipping 22 matching lines @@
         subcommands.CommandRunBase
 }
 
 func (cr *verifyCommandRun) Run(app subcommands.Application, args []string, env subcommands.Env) int {
         c := cli.GetContext(app, cr, env)
         a := getApplication(c, args)
 
         return run(c, func(c context.Context) error {
                 // Make sure that we can resolve the referenced specifiction.
                 if err := a.opts.ResolveSpec(c); err != nil {
-                        return errors.Annotate(err).Reason("failed to resolve specification").Err()
+                        return errors.Annotate(err, "failed to resolve specification").Err()
                 }
 
                 s := a.opts.EnvConfig.Spec
                 if s == nil {
                         s = &vpython.Spec{}
                 }
                 if s.Virtualenv == nil {
                         s.Virtualenv = &a.opts.EnvConfig.Package
                 }
 
                 // Verify that the spec can be normalized. This may modify it, so we will
                 // normalize a clone.
                 if err := spec.NormalizeSpec(s.Clone(), nil); err != nil {
-                        return errors.Annotate(err).Reason("failed to normalize specification").Err()
+                        return errors.Annotate(err, "failed to normalize specification").Err()
                 }
 
                 renderedSpec := spec.Render(s)
                 logging.Infof(c, "Successfully verified specification:\n%s", renderedSpec)
 
                 // Run our Verification generator and verify each generated environment.
                 if a.WithVerificationConfig != nil {
                         err := a.WithVerificationConfig(c, func(cfg Config, verificationScenarios []*vpython.PEP425Tag) error {
                                 if len(s.VerifyPep425Tag) > 0 {
                                         verificationScenarios = s.VerifyPep425Tag
@@ skipping 31 matching lines @@
                                 return nil
                         })
                         if err != nil {
                                 return err
                         }
                 }
 
                 return nil
         })
 }