The message about the bundling of the zsh completion with brew with their 1.0 release keeps showing up.
It says at the end that this message will only appear once, however I have now seen it for the last week or so.

Any idea why that happens?

OSX 10.12
iTerm2
Homebrew 1.0.9
Homebrew/homebrew-core (git revision 3927; last commit 2016-11-06)