core: Fix dyslexic/backward handling of 403/404 errors

server/fileserver.go

@@ -42,9 +42,9 @@ func (fh *fileHandler) serveFile(w http.ResponseWriter, r *http.Request, name st
 	f, err := fh.root.Open(name)
 	if err != nil {
 		if os.IsNotExist(err) {
-			return http.StatusForbidden, err
-		} else if os.IsPermission(err) {
 			return http.StatusNotFound, nil
+		} else if os.IsPermission(err) {
+			return http.StatusForbidden, err
 		}
 		// Likely the server is under load and ran out of file descriptors
 		w.Header().Set("Retry-After", "5") // TODO: 5 seconds enough delay? Or too much?
@@ -54,10 +54,10 @@ func (fh *fileHandler) serveFile(w http.ResponseWriter, r *http.Request, name st
 
 	d, err1 := f.Stat()
 	if err1 != nil {
-		if os.IsPermission(err) {
-			return http.StatusForbidden, err
-		} else if os.IsNotExist(err) {
+		if os.IsNotExist(err) {
 			return http.StatusNotFound, nil
+		} else if os.IsPermission(err) {
+			return http.StatusForbidden, err
 		}
 		// Return a different status code than above so as to distinguish these cases
 		return http.StatusInternalServerError, err