Parallels Plesk Panel 11 RPC API, part 2

My adventures with Parallels Plesk Panel's API continued. My previous fumblings can be found here. A fully working application started to say:

11003: PleskAPIInvalidSecretKeyException : Invalid secret key usage. Please check logs for details.

Ok. What does that mean? Google (my new favorite company) found nothing with that phrase or error code. Where is the log they refer to?

After a while I bumped into /usr/local/psa/admin/logs/panel.log. It said:

2013-10-16T11:34:35+03:00 ERR (3)  [panel]: Somebody tries to use the secret key for API RPC "-my-super-secret-API-key-" from "2001:-my-IPv6-address-"

Doing a:

/usr/local/psa/bin/secret_key --list

revealed that previously they accepted an IPv4 address for secret key, but apparenly one of those Micro-Updates changed the internal policy to start using IPv6 if one is available.

When I realized that, it was an easy fix. The log displayed the IP-address, I just created a new API-key with secret_key-utility and everything started to work again.

Parallels: Document your changes and error codes, please.