As discussed here, if an apt PPA changes its label and we try to apt-get update, we get something like this:
E: Repository 'http://ppa.launchpad.net/ondrej/php/ubuntu artful InRelease' changed its 'Label' value from '*****
The main PPA for PHP (5.6, 7.0, 7.1) with many PECL extensions *****' to '*****
The main PPA for supported PHP versions with many PECL extensions *****'
N: This must be accepted explicitly before updates for this repository can be applied.
See apt-secure(8) manpage for details."
The solution is to run apt update instead and manually accept the change.
This question is about the reasoning. Why is it important that the label does not change without my explicit awareness? I don't know where I would even see this label in normal day-to-day usage...