Area configuration aggregation… 5/7 [====================>-------] 71% 2 mins 368.0 MiB
[ReflectionException]
Class Not_Existing_Class does not exist
it is a Windows-only Magento 2.0.x bug.
It is fixed in Magento >= 2.1.0.
You can fix in manually in Magento 2.0.x:
https://github.com/magento/magento2/commit/e07ce736