Understanding error output when a subkey expires

[jman]

Ingo Klöcker <kloecker at kde.org> writes:

>> - [GNUPG:] KEY_CONSIDERED <fingerprint> 3 (what does the 3 stand for?)
>> - [GNUPG:] INV_SGNR 9
>> - [GNUPG:] FAILURE sign 54

Thank you Ingo for the useful explaination. Just a few additional notes (mostly for my own 
curiosity).

- "KEY_CONSIDERED <fingerprint> 3"
uses a flag (3) which is not documented (afaics)

- "INV_SGNR 9" means "unusable sender, Not a secret key"
I expected the error to be "Key expired"?

- "FAILURE sign 54" means "failure to sign"
the error code is also not documented

General thought: I see a debug info that I find a bit confusing and I need to go to the source code 
repository to get some clues, so as a user I wish gnupg could emit less confusing a little more 
/human/ parsable info.

Best,