[errors] Greatly simplify common/errors package.

vpython/application/subcommand_verify.go

Index: vpython/application/subcommand_verify.go
diff --git a/vpython/application/subcommand_verify.go b/vpython/application/subcommand_verify.go
index 47e7e5011a2e003ce2d59dd2c0e29352ca42825a..6fd3831206239f34ce46c6315348ccc87f16957b 100644
--- a/vpython/application/subcommand_verify.go
+++ b/vpython/application/subcommand_verify.go
@@ -40,7 +40,7 @@ func (cr *verifyCommandRun) Run(app subcommands.Application, args []string, env
 	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
@@ -54,7 +54,7 @@ func (cr *verifyCommandRun) Run(app subcommands.Application, args []string, env
 		// 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)