[pkg] Tidy substvars usage in control file The documentation package was missing a Built-Using field to record the provenance of the templates. Empty packages or meta packages do not require Depends on a specific Python version, so we can remove the relevant substvars.

Cubes
=====

This chapter describes how to define your own cubes and reuse already available cubes.

.. toctree::
   :maxdepth: 1

   layout.rst
   cc-newcube.rst
   available-cubes.rst