protected function mergePackagesConfig()
    {
        $this->getInstaller()
             ->mergeConfigData(
                 'packages.local',
                 include __DIR__ . '/../../../../config/default.packages.php',
                 function ( & $config )
                 {
                     if ( ! empty( $config['modules']['Grid\Core']['enabledPackages'] ) )
                     {
                         foreach ( $config['modules']['Grid\Core']['enabledPackages'] as & $packages )
                         {
                             if ( ! is_array( $packages ) )
                             {
                                 $packages = array(
                                     $packages => (string) $packages
                                 );
                             }

                             $packages = array_unique( array_map(
                                 'strtolower',
                                 array_filter(
                                     $packages,
                                     function ( $package )
                                     {
                                         return (bool) preg_match(
                                             '#^[a-z0-9_-]+/[a-z0-9_-]+$#i',
                                             $package
                                         );
                                     }
                                 )
                             ) );
                         }
                     }

                     return $config;
                 }
             );
    }