During Magento 2 upgrade process from 2.1.7 to Magento 2.1.8, when I run command: `php bin/magento setup:upgrade`
I was getting below error:

> 
> Cannot instantiate interface
>  Magento\Framework\App\Config\ConfigSourceInterface in
>  /home/public\_html/vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php:73
> 
> 
>