Catch a scenario in which the SKU table entries have been created, but the handler class hasn't been deployed yet

Summary: Our new namespace deployed master, therefor creating skus entries, but without the handler classes being available on actual production.

Test Plan: None

Reviewers: #hkccp_developers, machniak

Reviewed By: #hkccp_developers, machniak

Subscribers: #hkccp_developers

Differential Revision: https://git.kolab.org/D1834