Integration tests convenience nginx should listen to ipv6 too.

test/nginx.conf

@@ -4,7 +4,7 @@ events {
 
 http {
   server {
-    listen 8081;
+    listen [::]:8081 ipv6only=off;
 
     location ~ ^/_matrix/client/(r0|v3)/rooms/([^/]*)/report/(.*)$ {
       # Abuse reports should be sent to Mjölnir.