Timeout failures on Mac

Created by: Zaharid

Builds such as

https://travis-ci.com/github/NNPDF/nnpdf/jobs/297860674

are failing with

No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself.
Check the details on how to adjust your build configuration on: https://docs.travis-ci.com/user/common-build-problems/#Build-times-out-because-no-output-was-received

The build has been terminated

It would be good if someone with a Mac could investigate what is taking so long and if it is a genuine problem or Mac VMs being slow.