Using a tool with as many moving parts as webpack can come with its own headaches; mismatched versions of loaders, missing configurations etc. This error can happen often as a result of having webpack installed globally.
This is the full error message:
module.js:549 throw err; ^ Error: Cannot find module 'webpack/schemas/WebpackOptions.json' at Function.Module._resolveFilename (module.js:547:15) at Function.Module._load (module.js:474:25) at Module.require (module.js:596:17)
Here's a quick fix:
npm uninstall -g webpack webpack-cli npm install webpack webpack-cli --save-dev