In order to use `{{ dump(whatever) }}` in twig templates in Pattern Lab, you must enable twig debugging. Otherwise trying to use dump will blow up the `php .pattern-lab/core/console --generate` process. (If that happens when you're running it via gulp, it may fail silently :P)
Anyhow, to enable twig debugging, toggle `twigDebug` to `true` in /config/config.yml in the pattern lab app folder.