Use the "legacy" AuthenticationException

Emby.Server.Implementations/HttpServer/Security/AuthService.cs

@@ -2,9 +2,9 @@
 
 using System;
 using System.Linq;
-using System.Security.Authentication;
 using Emby.Server.Implementations.SocketSharp;
 using MediaBrowser.Common.Net;
+using MediaBrowser.Controller.Authentication;
 using MediaBrowser.Controller.Configuration;
 using MediaBrowser.Controller.Entities;
 using MediaBrowser.Controller.Net;