// app/AppKernel.php

class AppKernel extends Kernel
{
    public function registerBundles()
    {
        //...
        if (in_array($this->getEnvironment(), ['dev', 'test'])) {
            // ...
            // Because the vendor code could be not present, you should check if the bundle is here before using it.
            new Janalis\Doctrineviz\DoctrinevizBundle(),
        }


        // ...
    }

    // ...
}