Use registryHTTPResponseToError on /tags/list failure

We should have been doing that from the start, in order to
get server-reported errors correctly.

Also start using fmt.Errorf("...: %w") to get closer to Go
mainstream, now that this exists.

NOTE: This can break existing clients, notably (skopeo inspect)
which greps the error string for 401 and 403.

Sadly we don't have precise records of the original failures, so
there's no way to test; we'll just have to break them and see.

Signed-off-by: Miloslav Trmač <[email protected]>

docker/docker_image.go

@@ -73,8 +73,8 @@ func GetRepositoryTags(ctx context.Context, sys *types.SystemContext, ref types.
 			return nil, err
 		}
 		defer res.Body.Close()
-		if err := httpResponseToError(res, "fetching tags list"); err != nil {
-			return nil, err
+		if res.StatusCode != http.StatusOK {
+			return nil, fmt.Errorf("fetching tags list: %w", registryHTTPResponseToError(res))
 		}
 
 		var tagsHolder struct {