gulp - what's the problem?

Question

css

Good afternoon. I can not understand what the problem is, the code and the screen are attached. I will be very glad for help.
Problem:

GulpJS:

'use strict';

var gulp = require('gulp'),
    watch = require('gulp-watch'),
    prefixer = require('gulp-autoprefixer'),
    uglify = require('gulp-uglify'),
    sass = require('gulp-sass'),
    rigger = require('gulp-rigger'),
    cssmin = require('gulp-minify-css'),
    gs = require('gulp-selectors'),
    htmlmin = require('gulp-htmlmin'),
    uncss = require('gulp-uncss'),
    browserSync = require("browser-sync"),
    reload = browserSync.reload;

var path = {
    build: {
        html: 'build/',
        js: 'build/js/',
        css: 'build/css/',
        img: 'build/img/',
        fonts: 'build/fonts/'
    },
    src: {
        html: 'src/**/*.html',
        js: 'src/js/**/*.*',
        css: 'src/css/**/*.*',
        img: 'src/img/**/*.*',
        fonts: 'src/fonts/**/*.*'
    },
    watch: {
        html: 'src/**/*.html',
        js: 'src/js/**/*.js',
        style: 'src/css/**/*.scss',
        img: 'src/img/**/*.*',
        fonts: 'src/fonts/**/*.*'
    },
    clean: './build'
};

var config = {
    server: {
        baseDir: "./build"
    },
    tunnel: true,
    host: 'localhost',
    port: 9000,
    logPrefix: "The_Story"
};

gulp.task('webserver', function () {
    browserSync(config);
});


gulp.task('html:build', function () {
    gulp.src(path.src.html)
        .pipe(rigger())
        .pipe(htmlmin({collapseWhitespace: true}))
        .pipe(gulp.dest(path.build.html))
        .pipe(reload({stream: true}));
});

gulp.task('js:build', function () {
    gulp.src(path.src.js)
        .pipe(rigger())
        .pipe(uglify())
        .pipe(gulp.dest(path.build.js))
        .pipe(reload({stream: true}));
});

gulp.task('css:build', function () {
    gulp.src(path.src.css)
        .pipe(sass({
            sourceMap: true,
            errLogToConsole: true
        }))
        .pipe(prefixer())
        .pipe(uncss({
            html: ['src/**/*.html']
        }))
        .pipe(cssmin())
        .pipe(gs.run())
        .pipe(gulp.dest(path.build.css))
        .pipe(reload({stream: true}));
});

gulp.task('fonts:build', function() {
    gulp.src(path.src.fonts)
        .pipe(gulp.dest(path.build.fonts))
});

gulp.task('build', [
    'html:build',
    'js:build',
    'css:build',
    'fonts:build',
]);


gulp.task('watch', function(){
    watch([path.watch.html], function(event, cb) {
        gulp.start('html:build');
    });
    watch([path.watch.css], function(event, cb) {
        gulp.start('css:build');
    });
    watch([path.watch.js], function(event, cb) {
        gulp.start('js:build');
    });
    watch([path.watch.fonts], function(event, cb) {
        gulp.start('fonts:build');
    });
});


gulp.task('default', ['build', 'webserver', 'watch']);

Answer 1

watch([path.watch.css]
replaced by
watch([path.watch.style]