Brew recently started refusing to install anything if your xcode is out of date, and forces you to wait for a "brew update" if it hasn't updated in 24 hours. It's actually hideously user-unfriendly, but it probably saves the devs a lot of stupid github issues.

Unless you made the mistake of upgrading to Xcode 8 while staying with El Capitan and then wondering, why nothing works.

What specifically doesn't work?

It's working for me but I would love to have an example of breakage to take to my IT as another reason they should allow the company machines to be updated.