APT repository signing key needs to be manually updated on client side in order to extend expiration date

A few hour ago I had:

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://dist.keybase.io/linux/deb/repo stable InRelease: The following signatures were invalid: EXPKEYSIG 47484E50656D16C7 Keybase.io Code Signing (v1) <code@keybase.io>
W: Failed to fetch http://dist.keybase.io/linux/deb/repo/dists/stable/InRelease  The following signatures were invalid: EXPKEYSIG 47484E50656D16C7 Keybase.io Code Signing (v1) <code@keybase.io>
W: Some index files failed to download. They have been ignored, or old ones used instead.

It seems the initial key was created with an expiration date of 4 years, expiring on 2017-11-19 and that the expiration date has been extended for 14 more years very recently (on 2017-11-13): see output of gpg --list-packets code_signing_key.asc here: https://haste.zertrin.org/raw/golotegofa

If the key was added by apt-key add prior to 2017-11-13, it will not have the new signature from the current published GPG key, thus requiring user to understand what's going on (it took me almost an hour to figure it out, including the time to figure out how to print details from gpg commend about the key) and take manual action:

• download code_signing_key.asc
• sudo apt-key add code_signing_key.asc

Suggestion: better communicate when manual action is required, for example on https://keybase.io/blog

Start by reproducing the APT failure using the reported EXPKEYSIG output and review code_signing_key.asc with gpg --list-packets. Read the linked Keybase blog context and determine where users are told about key expiration and renewal; done means the required client-side action is clearly documented.