Ban SemrushBot for good inside nginx

Up to 2 weeks to fetch an update for robots.txt? Let's do it the quick way

modules/varnish/templates/mediawiki.conf

@@ -49,6 +49,11 @@ server {
 	if ($http_user_agent ~ "OpenVAS 8.0.9") {
 		return 403;
 	}
+
+	# Way too much traffic.
+	if ($http_user_agent ~ "SemrushBot") {
+		return 403;
+	}
 
 	location / {
 		proxy_pass http://127.0.0.1:81;
@@ -122,6 +127,11 @@ server {
 		return 403;
 	}
 
+	# Way too much traffic.
+	if ($http_user_agent ~ "SemrushBot") {
+		return 403;
+	}
+
 	<% if property['hsts'] == "strict" %>
 	add_header Strict-Transport-Security "max-age=15768000; includeSubDomains; preload";
 	<% else %>