project-system: VS2017RC3 - Assembly conflicts because of the same name

I have an interesting situation: I have a project called Newtonsoft.Json that I want to test in netcoreapp1.0, but the Microsoft.NET.Test.Sdk package that I have to depend on to run tests has a dependency on a NuGet package called Newtonsoft.Json.

I get this warning when I build in VS2017RC3:

Warning MSB3243 No way to resolve conflict between “Newtonsoft.Json, Version=9.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed” and “Newtonsoft.Json, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null”. Choosing “Newtonsoft.Json, Version=9.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed” arbitrarily.

And lots of this error:

error CS0433: The type ‘JsonConstructorAttribute’ exists in both ‘Newtonsoft.Json, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null’ and ‘Newtonsoft.Json, Version=9.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed’

How do I tell the Roslyn/msbuild/.NET Core that I want the referenced Newtonsoft.Json project to be used?