The MathTest fatal Error occurs, when using Toolchain 14.23 and updated of Visual Studio.
Load the Toolchain 14.22 (via VisualStudio Installer).
Then, search for the “UEBuildWindows.cs” File and change Line 563 to:
static readonly VersionNumber DefaultVisualStudioToolChainVersion = VersionNumber.Parse("14.22.27905");
Compile and it should work.
Remember, to put
BuildEnvironment = TargetBuildEnvironment.Unique;
bCompileChaos = true;
into your MyProjectEditor.Target.cs, too… if you want to use Chaos in an existing Project.