Do you have an idea when you would try to fix this? Within the next weeks or
rather months?

You mean you want something like EACCES instead of an empty listing? I am not
sure whether this is the right thing to do. Can please you describe your use case?

I think it would be the right thing.

I'm developing Schleuder, the OpenPGP-featuring mailing list manager.
If I'm receiving an empty list of public keys from GPGME I currently don't know
if there are no keys, or if the keyring couldn't be read. Thus I can't properly
decide what to do: try to fetch keys? I would run into the same problem when
trying to import them. Return an error message? Which one?

This has led repeatedly to confusion e.g. when people imported a key into a
schleuder-list's keyring in the shell as root, which results in changed
ownership of the keyring-files by gpg. Next Schleuder couldn't read the keyring
anymore and maybe refused operation because it couldn't verify any incoming
email any more — instead of giving a helpful error message that points to the
cause: lacking filesystem permissions.

Currently my only chance is to manually check the permissions of all files that
might be involved in an operation. That is working around a bug, in my eyes.

I agree that this is a practical problem.

With the soon to be released gnupg 2.1.16 and gpgme 1.8 this will work.

If a keyring is non-readable (e.g. chmod 000 pubring.bkx), gpgme_op_keylist_next
will return GPG_ERR_OPENKEYRING instead of GPG_ERR_EOF.