p11: return predefined errors

[bonifaido]

Signed-off-by: Nandor Kracser bonifaido@gmail.com

This helps to identify errors from the corresponding calls, which might be a bit more Go "idiomatic" maybe.

[langbeck]

I would like to have this feature as well. Specially for errors like ErrNoObjectsFound to properly check if a matching object exists.
@miekg could you have a look at this?
@bonifaido I think you need to add him as reviewer so the activity stands out on its "Recent activity"

[bonifaido]

You can't assign someone from a fork for reviewing (or at least I have no idea how to do that!). But your mention should be a correct ping I guess.

[langbeck]

@bonifaido yes, you can. The owner of the PR can add someone as reviewer.
At least I was able to do so when I opened #133

[bonifaido]

The Reviewers button is not clickable by me.

[bonifaido]

@miekg - excuse meg for the ping, any chance to review/merge this one?