Check for existence of vendor directory for better error message (#1301)

symfony/console/5.3/bin/console

@@ -4,6 +4,10 @@
 use App\Kernel;
 use Symfony\Bundle\FrameworkBundle\Console\Application;
 
+if (!is_dir(dirname(__DIR__).'/vendor')) {
+    throw new LogicException('Dependencies are missing. Try running "composer install".');
+}
+
 if (!is_file(dirname(__DIR__).'/vendor/autoload_runtime.php')) {
     throw new LogicException('Symfony Runtime is missing. Try running "composer require symfony/runtime".');
 }