Gulpfile Not found

[ERROR] Gulpfile (or dependent module) not found: ./gulpfile.js

    For custom Gulpfile locations, you can run ionic config set gulp.file <path>. Otherwise, the default 
    Ionic Gulpfile can be downloaded from
    Or, if you don't use gulp, you can disable it by running ionic config set gulp.enabled false.
    Full error:
    Error: Cannot find module 'gulp-sass'
        at Function.Module._resolveFilename (module.js:555:15)
        at Function.Module._load (module.js:482:25)
        at Module.require (module.js:604:17)
        at require (internal/module.js:11:18)
        at Object.<anonymous> (/home/logiciel1/Desktop/myApp/gulpfile.js:2:12)
        at Module._compile (module.js:660:30)
        at Object.Module._extensions..js (module.js:671:10)
        at Module.load (module.js:573:32)
        at tryModuleLoad (module.js:513:12)
        at Function.Module._load (module.js:505:3)