Don\'t double-close.

fs/contrib/archivefs.py

@@ -186,8 +186,9 @@ class ArchiveMountFS(mountfs.MountFS):
     @synchronize
     def close(self):
         # Close and delete references to any other fs instances.
-        self.rootfs.close()
-        self.rootfs = None
+        if self.rootsfs is not None:
+            self.rootfs.close()
+            self.rootfs = None
         super(ArchiveMountFS, self).close()
 
     def ismount(self, path):