public function addManagedExtensions()
    {
        if ($this->loaded) {
            throw new \RuntimeException('Extensions already loaded.');
        }

        try {
            $this->extFs->includeFile('vendor/autoload.php');
        } catch (FileNotFoundException $e) {
            $this->loaded = true;

            return;
        }

        $descriptors = $this->loadPackageDescriptors();
        foreach ($descriptors as $descriptor) {
            // Skip loading if marked invalid
            if ($descriptor->isValid() === false) {
                continue;
            }
            $this->addManagedExtension($descriptor);
        }
    }