Can't execute the task

[polikin]

When I try to run the task, this is the error I have:

(node:3748) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): undefined:20:103465: property missing ':'
(node:3748) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Structure:

gulp.src(config.path.instanceRoot + '/Website/public/css/styles.css')
        .pipe(criticalCss({
            out: 'critical.css',
            url: 'http://localhost/',
            width: 1280,
            height: 800,
            strict: true,
            userAgent: 'Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)'
        }))
        .pipe(cssnano())
        .pipe(gulp.dest(config.path.instanceRoot + '/Website/public/css'));

node: 8.9.4
gulp CLI version: 2.0.1