Fork https://github.com/collective/collective.jstraining and clone it with git, and install Plone by executing the following commands:
git clone <location of your fork> cd collective.jstraining ./bootstrap.sh
<location of your fork> should be replaced with where your fork is.
npm/nodejs install on your system
webpack installed on your system
grunt-cli installed on your system(
npm install -g grunt-cli)
On macOS versions of npm/nodejs newer than 6.9.1 can make the bundling process fail. Installing and using version 6.9.1 fixes the problem. Different versions of nodejs can be managed with nvm (Node Version Manager).