WSA System.IO.Directory Error Referenced from Assembly-UnityScript at System.Void ScreenshotMovie::Start()

Hy there,

I'm currently porting an existing game and building it for WSA Windows Phone 8.1 my build settings are

Type: XAML C# Solution

SDK: Phone 8.1

Use Net Core Partially

Using .Net 2.0

Unity 4.7.0f1

So know there is a problem when I build. It gives me errors that System.IO.Directory doesn't exist in the target framework and I'm totally aware of this fact but the app runs just fine and it still says I'm using it in the following

 Reference Rewriter: Error: type `System.IO.Directory` doesn't exist in target framework. It is referenced from Assembly-UnityScript at System.Void ScreenshotMovie::Start().

 Reference Rewriter: Error: method `System.Boolean System.IO.Directory::Exists(System.String)` doesn't exist in target framework. It is referenced from Assembly-UnityScript at System.Void ScreenshotMovie::Start().

 Reference Rewriter: Error: type `System.IO.Directory` doesn't exist in target framework. It is referenced from Assembly-UnityScript at System.Void ScreenshotMovie::Start().

 Reference Rewriter: Error: type `System.IO.DirectoryInfo` doesn't exist in target framework. It is referenced from Assembly-UnityScript at System.Void ScreenshotMovie::Start().

 Reference Rewriter: Error: method `System.IO.DirectoryInfo System.IO.Directory::CreateDirectory(System.String)` doesn't exist in target framework. It is referenced from Assembly-UnityScript at System.Void ScreenshotMovie::Start(). 

Complete error message

 UnityEngine.Debug:LogError(Object)
 PostProcessMetroPlayer:RunReferenceRewriter(MetroSDK, String, String, String, String) (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/PostProcessMetroPlayer.cs:489)
 PostProcessMetroPlayer:PostProcessSDKSpecific(MetroSDK, BuildTarget, BuildOptions, String, String, ProjectImages) (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/PostProcessMetroPlayer.cs:1007)
 PostProcessMetroPlayer:PostProcess(BuildTarget, BuildOptions, String, String, String, String) (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/PostProcessMetroPlayer.cs:740)
 UnityEditor.HostView:OnGUI()

I have personally no idea where this ScreenshotMovie::Start() function is and how I can change it to work with the System.IO for WSA apps and these errors make the Windows Certification Process fail although the app is just working fine without errors. So I would love some tips about it or someone telling me I'm overlooking something very stupid because I don't have any clue.