commit 3a00e5fcc1af121dea16793d47627c16c97fb953
Author: Christopher Faulet <cfaulet@haproxy.com>
Date:   Wed Nov 27 11:22:37 2019 +0100

    BUG/MINOR: contrib/prometheus-exporter: Use HTX errors and not legacy ones
    
    This bug was introduced when the commit 32d634f1 ("MINOR:
    contrib/prometheus-exporter: filter exported metrics by scope") was backported
    to 2.0.
    
    In 2.0, Error chunks exist in raw format (http_err_chunks[]) and in HTX format
    (htx_err_chunks[]). Prometheus exported only supports the HTX. So error must not
    be reported using the raw chunks.
    
    This fix is specific to 2.0. No backport needed.

diff --git a/contrib/prometheus-exporter/service-prometheus.c b/contrib/prometheus-exporter/service-prometheus.c
index 56d49a39..cfbfb8c3 100644
--- a/contrib/prometheus-exporter/service-prometheus.c
+++ b/contrib/prometheus-exporter/service-prometheus.c
@@ -2292,7 +2292,7 @@ static int promex_parse_uri(struct appctx *appctx, struct stream_interface *si)
 	return 1;
 
   error:
-	err = &http_err_chunks[HTTP_ERR_400];
+	err = &htx_err_chunks[HTTP_ERR_400];
 	channel_erase(res);
 	res->buf.data = b_data(err);
 	memcpy(res->buf.area, b_head(err), b_data(err));