Improve error message for unknown error in validateTargetRef

[RadaBDimitrova]

What type of PR is this?

What this PR does / why we need it:

This PR improves the info given when met with an "unknown error" during validateTargetRef since there have been multiple occasions where I've seen the following error and there are multiple paths in the code that could possibly lead to it:

Unknown error during checking if target is a topmost well-known or scalable controller: %!s(<nil>) with reason VerticalPodAutoscalerUnhealthy

Up until now there's a possibility to print a nil err, which doesn't really help with debugging the actual problem.

Which issue(s) this PR fixes:

N/A

Special notes for your reviewer:

/cc @ialidzhikov

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

NONE

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @RadaBDimitrova. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[adrianmoisey]

/ok-to-test

[ialidzhikov]

/cc @vitanovs

[k8s-ci-robot]

@ialidzhikov: GitHub didn't allow me to request PR reviews from the following users: vitanovs.

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[vitanovs]

Thanks for catching the issue and providing a functional solution, it will definitely improve the debugging experience. :))

Giving a small suggestion from my side, regarding the logging format. Thanks!

[ialidzhikov]

/lgtm

[adrianmoisey]

/lgtm

/cc @omerap12

[omerap12]

Thanks!
/approve
/label tide/merge-method-squash

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ialidzhikov, omerap12, RadaBDimitrova

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• vertical-pod-autoscaler/OWNERS [omerap12]

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