Laravel Bug in latest update?

Question

Laravel

I have MAIL_DRIVER=mailgun
If I do this on a new Laravel:
I set authorization php artisan make:auth
I register and try to recover the password through notification in the queueing notifications
queue I made a custom notification.
php artisan make:notification MyResetPassword
Added to the User Model:

use App\Notifications\MyResetPassword as ResetPasswordNotification; // Тут MyResetPassword
class User extends Authenticatable
{
    use Notifiable;
........
    public function sendPasswordResetNotification($token)
    {
        $this->notify(new ResetPasswordNotification($token));
    }
}

Redis is up and running.
Worth "guzzlehttp/guzzle": "^6.2",
vendor I didn't touch! Reinstalled Laravel 3 times from scratch today.
But an error log is written to the failed_jobs table !

Symfony\Component\Debug\Exception\FatalThrowableError: Class 'GuzzleHttp\Client' not found in /data/wwwroot/vendor/laravel/framework/src/Illuminate/Mail/TransportManager.php:185

Why is Class 'GuzzleHttp\Client' not found if it exists...
BUT IF I DO WITHOUT - Queueing Then everything works.
That is, in custom notification:
class ResetPassword extends NotificationWorks
And like this:

class ResetPassword extends Notification implements ShouldQueue

Does not work...