Using NuGet prior to 4.x causes cryptic errors in MSBuild.Traversal

[kingerja]

NuGet 4.x is required for the <PackageReference items and if it isn't used then expected imports do not occur causing a cryptic error. Need to detect this condition in some way and error.

C:\Program Files (x86)\Microsoft Visual Studio 2017\MSBuild\15.0\bin\Microsoft.Common.CurrentVersion.targets(2630,7): error MSB4057: The target "CreateManife
stResourceNames" does not exist in the project. [d:\git\CBT.Modules\src\dirs.proj]