Fix cssUrl module resolvers to support node6+

webpack-utils/cssUrl.js

@@ -28,7 +28,7 @@ module.exports = function(loader) {
                         loader.exec(`
                             var __webpack_public_path__ = '${loader.options.output.publicPath}';
                             ${source}
-                        `) + urlPostfix(url)
+                        `, dirname) + urlPostfix(url)
                     )
                 ) : resolve(url)
             )

webpack.config.js

@@ -205,7 +205,7 @@ var webpackConfig = {
                                 // when @imported files may be processed mutiple times
                                 fileCache[filename] = new Promise((resolve, reject) =>
                                     this.loadModule(filename, (err, source) =>
-                                        err ? reject(err) : resolve(this.exec(source))
+                                        err ? reject(err) : resolve(this.exec(source, rootPath))
                                     )
                                 );
                             }