Handle forbidden error when checking for knative

Merged Alex Ives requested to merge alexives/119379/handle_http_error_instead_of_not_found into master

What does this MR do?

This change handles a 403 when the knative-serving namespace doesn't exist.

Fixes #119379 (closed) Relates to #55246 (closed)

Does this MR meet the acceptance criteria?

Conformity

Availability and Testing

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

  • Label as security and @ mention @gitlab-com/gl-security/appsec
  • The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
  • Security reports checked/validated by a reviewer from the AppSec team
Edited by Thong Kuah