fixed http 500 error.

NzbDrone.Common/DiskProvider.cs

@@ -24,6 +24,16 @@ namespace NzbDrone.Common
 
         private static readonly Logger Logger = LogManager.GetCurrentClassLogger();
 
+        public virtual DateTime GetLastDirectoryWrite(string path)
+        {
+            if (!FolderExists(path))
+            {
+                throw new DirectoryNotFoundException("Directory doesn't exist. " + path);
+            }
+
+            GetFiles(path, SearchOption.AllDirectories);
+        }
+
         public virtual bool FolderExists(string path)
         {
             return Directory.Exists(path);

NzbDrone.Core.Test/IndexerTests.cs

@@ -179,6 +179,7 @@ namespace NzbDrone.Core.Test
             Mocker.Resolve<TestUrlIndexer>().FetchRss();
 
             Mark500Inconclusive();
+            ExceptionVerification.IgnoreWarns();
         }
 
         [TestCase("simpsons", 21, 23)]
@@ -387,6 +388,7 @@ namespace NzbDrone.Core.Test
         {
             ExceptionVerification.MarkInconclusive(typeof(WebException));
             ExceptionVerification.MarkInconclusive("System.Net.WebException");
+            ExceptionVerification.MarkInconclusive("(503) Server Unavailable.");
         }
     }
 }