Improve error display when thrown inside Webpack.config.js

[weaverryan]

When an error is thrown inside WebpackConfig.js, it falls outside of the try-catch used inside of getWebpackConfig() (

webpack-encore/index.js

Lines 372 to 383 in 5ca96e9

	getWebpackConfig() {
	try {
	validator(webpackConfig);
	return configGenerator(webpackConfig);
	} catch (error) {
	// prettifies errors thrown by our library
	const pe = new PrettyError();
	console.log(pe.render(error));
	process.exit(1); // eslint-disable-line
	}

). This means the errors are really ugly :). If we're going to prettify the errors (which I like), we should do it also around the methods to WebpackConfig.js. We'll probably need to wrap each method in a try-catch (or do something clever to do this automatically).