Fixed some mono specific tests.

src/NzbDrone.Core/Update/InstallUpdateService.cs

@@ -147,13 +147,12 @@ namespace NzbDrone.Core.Update
 
             if (scriptPath.IsNullOrWhiteSpace())
             {
-                throw new ArgumentException("Update Script has not been defined");
+                throw new UpdateFailedException("Update Script has not been defined");
             }
 
             if (!_diskProvider.FileExists(scriptPath, StringComparison.Ordinal))
             {
-                var message = String.Format("Update Script: '{0}' does not exist", scriptPath);
-                throw new FileNotFoundException(message, scriptPath);
+                throw new UpdateFailedException("Update Script: '{0}' does not exist", scriptPath);
             }
 
             _logger.Info("Removing NzbDrone.Update");

src/NzbDrone.Mono.Test/DiskProviderTests/DiskProviderFixture.cs

@@ -1,4 +1,5 @@
-using Mono.Unix;
+using System;
+using Mono.Unix;
 using NUnit.Framework;
 using NzbDrone.Common.Test.DiskTests;
 
@@ -15,6 +16,11 @@ namespace NzbDrone.Mono.Test.DiskProviderTests
 
         protected override void SetWritePermissions(string path, bool writable)
         {
+            if (Environment.UserName == "root")
+            {
+                Assert.Inconclusive("Need non-root user to test write permissions.");
+            }
+
             // Remove Write permissions, we're still owner so we can clean it up, but we'll have to do that explicitly.
 
             var entry = UnixFileSystemInfo.GetFileSystemEntry(path);