CI errors of addons on Travis

Hello, since some time my addons are giving me errors when building for the mac platform. The addons work totally fine on my mac and it looks like a problem in the travis.yml file, like some wrong parameters.

This is the error that I am receiving:
https://travis-ci.org/edap/ofxRaycaster/jobs/481245368

Basically, it tries to update a lot of brew formulas and then it stops:

No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself.

This is my travis file:

I suspect that the parameter:

osx_image: xcode8

Is no longer supported by travis, and maybe I have to give a newer xcode version. Any ideas on how to fix it?

Looks oF repo use xcode9.4 now.
https://travis-ci.org/openframeworks/openFrameworks