protected function replaceLaravelServiceProviders($contents)
    {
        $strings = [
            'Illuminate\Mail\MailServiceProvider',
            'Illuminate\Queue\QueueServiceProvider'
        ];

        // Replacement to:
        //  - additionally support Google App Engine Queues,
        //  - additionally support Google App Engine Mail.
        $replacements = [
            'Shpasser\GaeSupportL5\Mail\MailServiceProvider',
            'Shpasser\GaeSupportL5\Queue\QueueServiceProvider'
        ];

        $modified = str_replace($strings, $replacements, $contents);

        if ($contents !== $modified) {
            $this->myCommand->info('Replaced the service providers in "config/app.php".');
        }

        return $modified;
    }