Fixes: #U4-919, we will just use real classes for extension methods and all custom file systems like the MediaFileSystem must inherit from

FileSystemWrapper

src/Umbraco.Core/IO/MediaFileSystem.cs

@@ -0,0 +1,17 @@
+using System.Linq;
+using System.Text;
+
+namespace Umbraco.Core.IO
+{
+	/// <summary>
+	/// A custom file system provider for media
+	/// </summary>
+	[FileSystemProvider("media")]
+	internal class MediaFileSystem : FileSystemWrapper
+	{
+		public MediaFileSystem(IFileSystem wrapped)
+			: base(wrapped)
+		{
+		}
+	}
+}