Error: Cannot resolve module 'babel-loader'

I found out why. I didn't have babel or babel-core in my package.json. Add them fixed the error.

  "devDependencies": {
    "babel": "^5.8.23",
    "babel-core": "^5.0.0",
    "babel-loader": "^5.3.2"
}

In my case, I had mis-spelled the loader while installing it, so make sure you install

babel-loader

NOT

bable-loader