Schema Registry misleading error message when unauthorized

[Benny93]

Description

When registering a new schema against the schema registry and I am not authorized I get a misleading error message:
invalid character '<' looking for beginning of value
Instead of 401 unauthorized.
Because
`defer resp.Body.Close()
if resp.StatusCode == 200 {
if err = json.NewDecoder(resp.Body).Decode(response); err != nil {
return err
}
return nil
}

var failure RestError
if err := json.NewDecoder(resp.Body).Decode(&failure); err != nil {
	return err
}

`
is parsing the response body as json right away.
In my case the unauthorized response body contains html.

How to reproduce

• Set the schema registry up to require authentication
• Register a new schema without credentials

Checklist

Please provide the following information:

• confluent-kafka-go and librdkafka version (LibraryVersion()): v2.3.0
• Apache Kafka broker version: quay.io/strimzi/kafka:0.38.0-kafka-3.6.0 / confluentinc/cp-schema-registry:7.0.9
• Client configuration: ConfigMap{...} :
• Operating system: Ubuntu 20.04.6 LTS (Focal Fossa)
• Provide client logs (with "debug": ".." as necessary)
• Provide broker log excerpts
• Critical issue