Abstraction violations in web/info.py

[davidsarah]

At source:src/allmydata/web/info.py?rev=4164#L92​ , we see

  if IDirectoryNode.providedBy(node):
      node = node._node

(and similarly in a few other methods of MoreInfo).

This is getting the underlying file node for a directory node, but it's doing it by getting the _node attribute, which follows the private instance variable convention. Probably there should be a method on IFilesystemNode to get the underlying file node (which would return self for non-directory nodes).