Imports possible without primary key

[indykoning]

Steps to reproduce

1. Remove the value of Akeneo attribute code for SKU from Attribute codes to import
2. Run an Akeneo import

Expected result

You would hope somewhere in the process of NOT importing your SKU attribute an error would be thrown.
Either as a failsafe during configuration, or a failsafe during the import itself.

Actual result

Instead the import continues as normal, however since no SKU is available from Akeneo the sku on all products are overwritten by the UUID