Revoked identity listed as valid

[sapk]

This isn't really a PR but we have have an issue on https://github.com/go-gitea/gitea/issues/6778 with a revoked identity being listed as valid. The goal is to find the reason and fix this in the PR.

So, I added a test with the user public key to confirm the bug. (If we found the exact reason I will generate a dummy one and rebase)

I haven't found the culprit so if you can have a look.

For the details, What version of Go are you using (go version)? 1.13 What operating system and processor architecture are you using? linux What did you do? use a key with revoked id and a valid one What did you expect to see? only the valid one What did you see instead? both ids

sidenote: I don't think it is bound to os/platform/go version.

Thanks in advance for any help you can provide.