[errors] Greatly simplify common/errors package.

logdog/client/cmd/logdog_butler/subcommand_run.go

Index: logdog/client/cmd/logdog_butler/subcommand_run.go
diff --git a/logdog/client/cmd/logdog_butler/subcommand_run.go b/logdog/client/cmd/logdog_butler/subcommand_run.go
index be5afa16a2f1f6590750b15a4589583d95f9b9e9..6ec39ae57a13a3bcce43a3feda8944d6f942ed99 100644
--- a/logdog/client/cmd/logdog_butler/subcommand_run.go
+++ b/logdog/client/cmd/logdog_butler/subcommand_run.go
@@ -305,19 +305,19 @@ func (cmd *runCommandRun) Run(app subcommands.Application, args []string, _ subc
 		// Add our pipes as direct streams, if configured.
 		if stdout != nil {
 			if err := b.AddStream(stdout, cmd.stdout.properties()); err != nil {
-				return errors.Annotate(err).Reason("failed to attach STDOUT pipe stream").Err()
+				return errors.Annotate(err, "failed to attach STDOUT pipe stream").Err()
 			}
 		}
 		if stderr != nil {
 			if err := b.AddStream(stderr, cmd.stderr.properties()); err != nil {
-				return errors.Annotate(err).Reason("failed to attach STDERR pipe stream").Err()
+				return errors.Annotate(err, "failed to attach STDERR pipe stream").Err()
 			}
 		}
 
 		// Execute the command. The bootstrapped application will begin executing
 		// in the background.
 		if err := proc.Start(); err != nil {
-			return errors.Annotate(err).Reason("failed to start bootstrapped process").Err()
+			return errors.Annotate(err, "failed to start bootstrapped process").Err()
 		}
 
 		// Wait for the process' streams to finish. We must do this before Wait()
@@ -345,7 +345,7 @@ func (cmd *runCommandRun) Run(app subcommands.Application, args []string, _ subc
 			if err == context.Canceled {
 				return err
 			}
-			return errors.Annotate(err).Reason("failed to Wait() for Butler").Err()
+			return errors.Annotate(err, "failed to Wait() for Butler").Err()
 		}
 
 		return nil
@@ -379,8 +379,8 @@ func (cmd *runCommandRun) maybeWriteResult(ctx context.Context, r *bootstrapResu
 		"path": cmd.resultPath,
 	}.Debugf(ctx, "Writing bootstrap result.")
 	if err := r.WriteJSON(cmd.resultPath); err != nil {
-		return errors.Annotate(err).Reason("failed to write JSON file").
-			D("path", cmd.resultPath).Err()
+		return errors.Annotate(err, "failed to write JSON file").
+			InternalReason("path(%s)", cmd.resultPath).Err()
 	}
 	return nil
 }