🐛 Ignore groups not served by the cluster

[jerr]

Description

If a group is not available on a server the discovery.ServerPreferredResources function returns the list of preferred resources but also an ErrGroupDiscoveryFailed error with the groups not available.

This error can be ignored because the unavailable resource types should not be audited.

This is an example of a cluster with the external.metrics.k8s.io group not available:

$ kubectl  get apiservice v1beta1.external.metrics.k8s.io 
NAME                              SERVICE                    AVAILABLE                      AGE
v1beta1.external.metrics.k8s.io   my-custom-metrics-server   False (FailedDiscoveryCheck)   22d

$ kubectl  get --raw /apis/external.metrics.k8s.io/v1beta1
Error from server (ServiceUnavailable): the server is currently unable to handle the request

If we have a cluster in this state no resources are audited because an error is returned by discovery.ServerPreferredResources

kubeaudit/internal/k8sinternal/client.go

Lines 129 to 130 in 6a30cc0

	lists, err := kc.ServerPreferredResources()
	if err == nil {

Type of change

• Bug fix 🐛

How Has This Been Tested?

• Automated tests still work
• Manual tests: The kubeaudit all command was tested on a cluster with an unavailable external.metrics.k8s.io group. Without this fix no reports are displayed, with the fix the reports are provided as expected.

Checklist:

• I have 🎩 my changes (A 🎩 specifically includes pulling down changes, setting them up, and manually testing the changed features and potential side effects to make sure nothing is broken)
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• The test coverage did not decrease
• I have signed the appropriate Contributor License Agreement

[genevieveluyt]

Thanks! Just an optional nit