Comment 1 for bug 1727021

/usr/local/Homebrew/Library/Homebrew/brew.rb:12:in `<main>': Homebrew must be run under Ruby 2.3! You're running 2.0.0. (RuntimeError)

Hm, indeed it does.

Looks like the same issue has hit multiple other projects (https://github.com/travis-ci/travis-ci/issues/8552, see in particular comment https://github.com/travis-ci/travis-ci/issues/8552#issuecomment-335430374 which explains the underlying issue). Apparently brew tries to autoupdate when installing packages and run into the error messages. The workaround for now is to update brew manually before installing packages, I'll soon push a branch where we can test this.

A proper fix might come with the new default osx images due soon https://blog.travis-ci.com/2017-10-16-a-new-default-os-x-image-is-coming so hopefully the workaround will be temporary...