Steps to reproduce:
1. Create new project
2. Switch platform to UWP
3. Change scripting backend to .NET
4. Build Project

Expected results: Project is successfully built.
Actual results: Project is successfully built, but also two errors are printed in the Console window

Reproduced with: 2018.3.0b3, 2018.3.0b1
Not reproducible with: 2018.3.0a11, 2018.2.8f1
Regression introduced in: 2018.3.0b1

Errors:
Reference Rewriter found some errors while running with command "--target=Temp\StagingArea\Unity.TextMeshPro.dll" "--target=Temp\StagingArea\UnityEngine.Timeline.dll" "--target=Temp\StagingArea\nunit.framework.dll" "--target=Temp\StagingArea\UnityEngine.UI.dll" "--target=Temp\StagingArea\UnityEngine.SpatialTracking.dll" "--target=Temp\StagingArea\UnityEngine.Networking.dll" "--target=Temp\StagingArea\UnityEngine.TestRunner.dll" <...>

Reference rewriter: Error: method `System.Reflection.FieldInfo System.Type::GetField(System.String,System.Reflection.BindingFlags)` doesn't exist in target framework. It is referenced from UnityEngine.TestRunner.dll at System.Reflection.FieldInfo UnityEngine.TestTools.EnumerableSetUpTearDownCommand::GetPCFieldInfo(System.Collections.IEnumerator).
UnityEngine.Debug:LogError(Object)
PostProcessWinRT:RunReferenceRewriter() (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/PostProcessWinRT.cs:1074)
PostProcessWinRT:Process() (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/PostProcessWinRT.cs:208)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)