Lately I've started hitting the below error on two build machines (Node 6.2.x and 6.3.x) and it was also reported here stylesuxx/generator-react-webpack-redux#45.
Module build failed: Error: Couldn't find preset "es2015" relative to directory "."
We might have to check whether something changed in the type of dependencies that lets babel-preset-es2015 miss all the sudden. If so we can add it to the devDependencies.