cpSpawn= require('child_process').spawn

gulp.task('update_nuget_packages', ['getSolutionName'], function() {
var nuget = spawn('./node_modules/nuget/bin/nuget.exe', ['update', './../yourSln.sln', '-prerelease', '-source', 'packageNugetSource']);
 
    nuget.stdout.on('data', (data) => {
        console.log(`${data}`);
    });
 
    nuget.stderr.on('data', (data) => {
        console.log(`Error: ${data}`);
    });
 
    nuget.on('close', (code) => {
        console.log(`child process exited with code ${code}`);
    });
});