The dev server (run via `yarn start`) doesn't pick up filesystem changes from the host, when run inside the VM. This is a known issue with virtualbox shared folders and can be worked around via: https://webpack.js.org/configuration/watch/#watchoptions-poll This saves people having to manually restart the dev server when doing full-stack development (which takes ~40s to start).

Commit pushed to master at https://github.com/mozilla/treeherder https://github.com/mozilla/treeherder/commit/a574f02161f9693079c4be62b9b96c26bfc5eb70 Bug 1461649 - Enable dev-server's polling watch mode in Vagrant (#3552) This allows the webpack-dev-server filesystem watching to work even inside Vagrant (such as when using `yarn start:local`), where the Virtualbox shared folders mean that standard inotify watching does not work: https://webpack.js.org/configuration/dev-server/#devserver-watchoptions-