ERROR in ./node_modules/css-loader!./node_modules/postcss-loader/lib!./node_modules/sass-loader/lib/loader.js!./sass/app.scss
    Module not found: Error: Can't resolve './ajax-loader.gif' in '/Users/Vishal/Documents/Work/nf-core/sass'
     @ ./node_modules/css-loader!./node_modules/postcss-loader/lib!./node_modules/sass-loader/lib/loader.js!./sass/app.scss 6:89679-89707

loaders: commonConfig.module.loaders.concat({
    test: /.s?css$/,
    exclude: /(node_modules)/,
    use: ExtractTextPlugin.extract({
        fallback: 'style-loader',
        use: ['css-loader', 'postcss-loader', 'sass-loader']
    })
})