chmod +x to the pre and post script! Travis-ci tests run by hosts within .travis.yum and your local should run well by
npm run-script local
You'll be asked for your sudo password, as the tests make a backup of your /etc/hosts file while it temporarily replaces it with the file hosts.
To be sure not to damage your system, the /etc/hosts is logged into .hosts.log within your current directory. You could edit, copy and paste the hosts back to /etc/hosts for repairing your system.