PHP AppKernel Symfony Issue

Note People have marked this question as simmilar to others, but its not =- I am not using symfony and doctrine as a web framework, I am using symfony components with doctrine while using Slimphp as the actual web framework.

So while you might think I need an AppKernel I don't. I am using symfony components. The only issue here is that @UniqueEntity isn't working.

I have no idea what I am doing. I am getting the error:

Fatal error: Class 'doctrine.orm.validator.unique' not found in /var/www/html/image_upload_app/vendor/symfony/validator/ConstraintValidatorFactory.php on line 46

My AppKernel.php looks like:

namespace ImageUploader;

use Symfony\Component\HttpKernel\Kernel;
use Symfony\Component\Config\Loader\LoaderInterface;

class AppKernel extends Kernel {

    public function registerBundles() {
        $bundles = array(
            new \Doctrine\Bundle\DoctrineBundle\DoctrineBundle()
        );

        return $bundles;
    }

    public function registerContainerConfiguration(LoaderInterface $loader) {}
}

From there I created a bootstrap.php with the following contents:

/** ---------------------------------------------------------------- **/
// Lets Setup Doctrine.
/** ---------------------------------------------------------------- **/
require_once 'vendor/autoload.php';

$loader = require 'vendor/autoload.php';
\Doctrine\Common\Annotations\AnnotationRegistry::registerLoader(array($loader, 'loadClass'));

use Doctrine\ORM\Tools\Setup;
use Doctrine\ORM\EntityManager;

/**
 * Set up Doctrine.
 */
class DoctrineSetup {

    /**
     * @var array $paths - where the entities live.
     */
    protected $paths = array(APP_MODELS);

    /**
     * @var bool $isDevMode - Are we considered "in development."
     */
    protected $isDevMode = false;

    /**
     * @var array $dbParams - The database paramters.
     */
    protected $dbParams = null;

    /**
     * Constructor to set some core values.
     */
    public function __construct(){
        if (!file_exists('db_config.ini')) {
            throw new \Exception(
                'Missing db_config.ini. You can create this from the db_config_sample.ini'
            );
        }

        $this->dbParams = array(
            'driver' => 'pdo_mysql',
            'user' => parse_ini_file('db_config.ini')['DB_USER'],
            'password' => parse_ini_file('db_config.ini')['DB_PASSWORD'],
            'dbname' => parse_ini_file('db_config.ini')['DB_NAME']
        );
    }

    /**
     * Get the entity manager for use through out the app.
     *
     * @return EntityManager
     */
    public function getEntityManager() {
        $config = Setup::createAnnotationMetadataConfiguration($this->paths, $this->isDevMode, null, null, false);
        return EntityManager::create($this->dbParams, $config);
    }
}

/**
 * Function that can be called through out the app.
 *
 * @return EntityManager
 */
function getEntityManager() {
    $ds = new DoctrineSetup();
    return $ds->getEntityManager();
}

/**
 * Function that returns the conection to the database.
 */
function getConnection() {
    $ds = new DoctrineSetup();
    return $ds->getEntityManager()->getConnection();
}

use \ImageUploader\AppKernel;

$kernel = new AppKernel();
$kernel->loadClassCache();

I am unsure why I keep getting this error, I have a model (entity) that looks as such:

namespace ImageUploader\Models;

use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Validator\Constraints as Assert;
use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;

/**
 * @ORM\Entity
 * @ORM\Table(name="users")
 * @UniqueEntity(fields="userName")
 * @UniqueEntity(fields="email")
 */
class User {

    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue
     */
    protected $id;

    /**
     * @ORM\Column(type="string", length=32, nullable=false)
     * @Assert\NotBlank()
     */
    protected $firstName;

    /**
     * @ORM\Column(type="string", length=32, nullable=false)
     * @Assert\NotBlank()
     */
    protected $lastName;

    /**
     * @ORM\Column(type="string", length=100, unique=true, nullable=false)
     * @Assert\NotBlank(
     *    message = "Username cannot be blank"
     * )
     */
    protected $userName;

    /**
     * @ORM\Column(type="string", length=100, unique=true, nullable=false)
     * @Assert\NotBlank()
     * @Assert\Email(
     *    message = "The email you entered is invalid.",
     *    checkMX = true
     * )
     */
    protected $email;

    /**
     * @ORM\Column(type="string", length=500, nullable=false)
     * @Assert\NotBlank(
     *  message = "The password field cannot be empty."
     * )
     */
    protected $password;

    /**
     * @ORM\Column(type="datetime", nullable=true)
     */
    protected $created_at;

    /**
     * @ORM\Column(type="datetime", nullable=true)
     */
    protected $updated_at;
}

when I go to validate the model, I get the error listed above. I have installed doctrine bundle and I thought I set things up properly. But apparently not. Does any know know what I am doing wrong? Did I configure something wrong or not configure something at all?