If you're using Webpack 2+ then you shouldn't need this plugin anymore. Under normal circumstances Webpack should already exit with a proper exit code. As such, this plugin does not officially support Webpack 2+.
If you don't get the correct exit code with Webpack 2+ then this is most likely a bug in a plugin you're using, or you're running into a Webpack bug. In either case I strongly recommend to isolate the problem and file issues at the appropriate repositories. In the mean time you could try to use this plugin as a temporary workaround.
Webpack plugin that will make the process return status code 1 when it finishes with errors in single-run mode.
npm install webpack-fail-plugin --save-dev
var failPlugin = ;moduleexports =//configplugins:failPlugin
Credits to @happypoulp.