The following was reported to gnupg-devel by dkg, but got no response. I'm
creating this issue to make sure it doesn't get lost.

gpg --check-trustdb normally sends no data to stdout, even if --verbose
is specfieid once. however, when i add --verbose --verbose it sends a
lot of data to stdout, in particular, lines like this:

0:F2AD85AC1E42B367:U:::f:::Werner Koch <wk@gnupg.org>:
[...]

I believe this also happens when the trustdb is automatically checked
(though i'm not sure how to force that to happen to test it better).

sending additional data to stdout during an automatic check (or even
during --check-trustdb when it's not otherwise expected) seems
problematic for anyone using the tool programmatically.