add traceError error

tool/error.go

 package tool
 
 import (
+	"fmt"
+	"runtime"
+
 	"github.com/juju/errors"
 )
 
 var Annotate = errors.Annotate
+
+func TraceError(err error, skip int) error {
+	if err == nil {
+		return nil
+	}
+	_, file, line, ok := runtime.Caller(skip + 1)
+	if !ok {
+		return err
+	}
+	return fmt.Errorf("%s:%d: %s", file, line, err)
+}