non-pkg: gofix -r error -force=error

R=golang-dev, iant, r, r
CC=golang-dev
https://golang.org/cl/5307066
diff --git a/doc/codewalk/urlpoll.go b/doc/codewalk/urlpoll.go
index b51be95..b320eb1 100644
--- a/doc/codewalk/urlpoll.go
+++ b/doc/codewalk/urlpoll.go
@@ -71,7 +71,7 @@
 	if err != nil {
 		log.Println("Error", r.url, err)
 		r.errCount++
-		return err.String()
+		return err.Error()
 	}
 	r.errCount = 0
 	return resp.Status