Log Message:
py-django-cms: updated to 3.5.3

3.5.3:
* Fixed TreeNode.DoesNotExist exception raised when exporting
  and loading database contents via dumpdata and loaddata.
* Fixed a bug where request.current_page would always be the public page,
  regardless of the toolbar status (draft / live). This only affected custom
  urls from an apphook.
* Removed extra quotation mark from the sideframe button template
* Fixed a bug where structureboard tried to preload markup when using legacy
  renderer
* Fixed a bug where updates on other tab are not correctly propagated if the
  operation was to move a plugin in the top level of same placeholder
* Fixed a bug where xframe options were processed by clickjacking middleware
  when page was served from cache, rather then get this value from cache
* Fixed a bug where cached page permissions overrides global permissions
* Fixed a bug where plugins that are not rendered in content wouldn't be
  editable in structure board
* Fixed a bug with expanding static placeholder by clicking on "Expand \ 
All" button
* Fixed a bug where descendant pages with a custom url would lose the overwritten
  url on save.
* Fixed a bug where setting the on_delete option on PlaceholderField
  and PageField fields would be ignored.
* Fixed a bug when deleting a modal from changelist inside a modal