Class Magento\Framework\Api\SearchCriteria\CollectionProcessorInterface does not exist
This error is related to the WeSupply Toolbox module, and only shows up on Magento 2.1.x when running php bin/magento setup:di:compile
If you receive this error on Magento 2.1.x, there are two solutions:
If you don't use the WeSupply Toolbox module, remove the whole WeSupply/Toolbox directory under app/code.
Note: Simply disabling the extension via bin/magento module:disable is not sufficient. The files need to be removed completely.
If you need to use the WeSupply Toolbox module, please upgrade your Magento version to 2.2.x or 2.3.x, as this error only shows on Magento 2.1.x.