如何使用没有作曲家和命名空间的记录器？

Question

I am trying to install Mangopay https://github.com/Mangopay/mangopay2-php-sdk, but the recommended solution of installing it without composer doesn't work. I used this line:

require_once "mango/mangopay2-php-sdk-2.11.0/MangoPay/Autoloader.php";
$api = new MangoPay\MangoPayApi();

The file get's loaded, but I get the following error:

Fatal error: Uncaught Error: Class 'Psr\Log\NullLogger' not found in 
/usr/local/apache2/htdocs/MangoPay/MangoPayApi.php:223 Stack trace: 
#0 /usr/local/apache2/htdocs/pay.php(5): MangoPay\MangoPayApi- 
>__construct() #1 {main} thrown in 
/usr/local/apache2/htdocs/MangoPay/MangoPayApi.php on line 223

The issue is with the logger, which I manually downloaded and copied into the directory but it still doesn't work. I am only asking here because I am not getting any response from the developers.

Any help with manually installing the logger and getting the namespace to work with mangopay is welcome.