         {
             dispatch_async(self.queue) {
                 
-                let fileURL = self.fileURLForKey(key: key)
-                
-                guard let filePath = fileURL.path
+                guard let filePath = self.fileURLForKey(key: key)?.path
                     else
                 {
-                    assertionFailure("no cache path found: \(fileURL)")
+                    assertionFailure("no cache path found")
                     
                     return
                 }

            return NSURL(fileURLWithPath: directory)
        }
        
        private func fileURLForKey(key key: String) -> NSURL
        {
            let directoryURL = self.cachesDirectoryURL()
            
            guard let fileURL = directoryURL.URLByAppendingPathComponent(key) else
            {
                fatalError("failed to create file URL")
            }
            
            return fileURL

                
                let fileManager = NSFileManager()
                
                guard let filePath = self.fileURLForKey(key: key)?.path
                    else
                {
                    assertionFailure("no cache path found")
                    
                    return
                }
