This the Mako 5 error handler as a stand-alone package that is ment to be used with Mako 4.5 applications running on PHP 7.
Install the package using composer:
composer require letron/error-compat
Then open your app/config/application.php
configuration file and replace the two Mako error handler services with the letron\error\services\cli\ErrorHandlerService
and letron\error\services\web\ErrorHandlerService
services.
That's it. You're done!