Error_template feature

Hi,

I need to customize the error message when something unexpected happens.
So for that validation, I´ve run kong on docker defined the error_default_type = text/html and error_template_html = xxx/yyy/error.html.
I´ve created a service that points to a non-valid upstream, but the error still appears in this way:

{ "message": "failed the initial dns/balancer resolve for 'echo-serverv2' with: dns lookup pool exceeded retries (1): timeout" }

What I am missing?

Error Logs
2023/06/12 18:50:58 [error] 103#0: *742 [lua] init.lua:388: execute(): DNS resolution failed: dns lookup pool exceeded retries (1): timeout. Tried: ["(short)echo-serverv2:(na) - cache-miss","echo-serverv2:1 - cache-miss/scheduled/querying/try 1 error: timeout/scheduled/querying/try 2 error: timeout/dns lookup pool exceeded retries (1): timeout","echo-serverv2:5 - cache-miss/scheduled/querying/try 1 error: timeout/scheduled/querying/try 2 error: timeout/dns lookup pool exceeded retries (1): timeout","echo-serverv2:33 - cache-miss/scheduled/querying/try 1 error: timeout/scheduled/querying/try 2 error: timeout/dns lookup pool exceeded retries (1): timeout"], client: 172.29.0.1, server: kong, request: "GET /v1/guestusers HTTP/1.1", host: "localhost:9101"

same here: error_template feature · Kong/kong · Discussion #11054 · GitHub

I believe you are trying to transform a response from upstream to custom message. Have you tried Response Transformation ?