Commented Unassigned: On Migration or Run I get: IsSystem' attribute is not declared. [1128]

<File Unknown>(0,0) : error 2025: XML Schema validation failed for mapping schema. Schema Error Information : The 'http://schemas.microsoft.com/ado/2012/10/edm/migrations:IsSystem' attribute is not declared..

How do I fix this?

Thanks!
Comments: How does this apply to unit-testing the EF framework itself? I can't run tests before submitting pulls.