Prevent ObjectManager from instantiating interface

[ldusan84]

I updated my local magento2 project and got: Fatal error: Cannot instantiate interface Mage_Core_Model_ConfigInterface

It seems that Object Manager is trying to instantiate an interface. I can look further into this if needed.

[antonkril]

Such situation happens if a class has a dependency on interface but implementation preference for that interface is not declared in configuration. If it happens after update, you should try:

1. clear cache :)
2. re-run compiler tool

Maybe we should add proper error message for such case.

[ldusan84]

You are right. Thanks.