Just ran into this issue with chrome package from Google: E: Repository 'http://dl.google.com/linux/chrome/deb stable Release' changed its 'Origin' value from 'Google, Inc.' to 'Google LLC' N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.
Rather than adding information to apt-secure's man page, I think it would be more helpful to output the command the user needs to accept the change: E: Repository 'http://dl.google.com/linux/chrome/deb stable Release' changed its 'Origin' value from 'Google, Inc.' to 'Google LLC' N: If you would like to accept this change, please rerun apt-get update with the `--allow-releaseinfo-change` flag