add should fail on 40x

Signed-off-by: Yoan Blanc <yoan@dosimple.ch>

integration/dockerfiles/Dockerfile_test_add_404

@@ -0,0 +1,4 @@
+FROM debian:9.11
+
+# Testing that any HTTP failure is handled properly
+ADD https://httpstat.us/404 .

pkg/util/fs_util.go

@@ -545,6 +545,11 @@ func DownloadFileToDest(rawurl, dest string, uid, gid int64) error {
 		return err
 	}
 	defer resp.Body.Close()
+
+	if resp.StatusCode >= 400 {
+		return fmt.Errorf("%s failed with %d", rawurl, resp.StatusCode)
+	}
+
 	if err := CreateFile(dest, resp.Body, 0600, uint32(uid), uint32(gid)); err != nil {
 		return err
 	}