Installer sonata admin-bundle

Bonjour ,
la jai installé les quatres dependances de sonata
quand j'execute     php app/console  assets:install web

il fait un fatal errors  genre: alors que j'ai mis block bundle dans AppKernel

C:\Users\Stagiaire>cd../..xampp/htdocs/symfony
Le chemin d'accès spécifié est introuvable.

C:\Users\Stagiaire>cd../../xampp/htdocs/symfony

C:\xampp\htdocs\Symfony>php app/console assets:install web

Fatal error: Class 'Sonata\BlockBundle\SonataBlockBundle' not found in C:\xampp\
htdocs\Symfony\app\AppKernel.php on line 23

Call Stack:
    0.0013     125136   1. {main}() C:\xampp\htdocs\Symfony\app\console:0
    0.7340    1330472   2. Symfony\Component\Console\Application->run() C:\xampp
\htdocs\Symfony\app\console:22
    0.8715    1477848   3. Symfony\Bundle\FrameworkBundle\Console\Application->d
oRun() C:\xampp\htdocs\Symfony\vendor\symfony\symfony\src\Symfony\Component\Cons
ole\Application.php:106
    0.8716    1477912   4. Symfony\Bundle\FrameworkBundle\Console\Application->r
egisterCommands() C:\xampp\htdocs\Symfony\vendor\symfony\symfony\src\Symfony\Bun
dle\FrameworkBundle\Console\Application.php:68
    0.8716    1477968   5. Symfony\Component\HttpKernel\Kernel->boot() C:\xampp\
htdocs\Symfony\vendor\symfony\symfony\src\Symfony\Bundle\FrameworkBundle\Console
\Application.php:83
    0.8716    1478048   6. Symfony\Component\HttpKernel\Kernel->initializeBundle
s() C:\xampp\htdocs\Symfony\app\bootstrap.php.cache:377
    0.8716    1478360   7. AppKernel->registerBundles() C:\xampp\htdocs\Symfony\
app\bootstrap.php.cache:543


C:\xampp\htdocs\Symfony>