NuGet throws "Unable to satisfy package dependency constraints" but no dependency is required in the package description

Question

I'm trying to update the following nuget packages :

• System.Collections.Immutable
• System.Reflection.Metadata (which only requires the previous package)

When doing so, I get an

"Unable to satisfy package dependency constraints"

error. But :

• On the System.Collections.Immutable package page, it is mentionned that no dependency is required
• Even after I've forced the update of the first one by selecting the Ignore dependency option, I still get the error for the second package

If I force both updates, when running my code,

the System.Reflection.Metadata raises an EntryPointNotFoundException : unable to find "ReadFile" entry point in api-ms-win-core-file-l1-2-0.dll.

For now, I would like to now why I can't update my packages in a normal way before investigating further the second problem.

I'm working on Windows 7 with Visual Studio 2015 RC and with NuGet 3.0

Thanks in advance for your help !

EDIT : I'm not sure this is a duplicate because in my case I get the error with a package which doesn't require any dependency.