Deprecation warnings

These deprecation warning probably should be resolved before it's too late.

The first two of them originate from imports in ecm.py. Not sure about the 'old styled index node' though.

/usr/lib/python3.8/importlib/__init__.py:127: RemovedInSphinx40Warning: sphinx.util.pycompat.htmlescape is deprecated. Check CHANGES for Sphinx API modifications.
  return _bootstrap._gcd_import(name[level:], package, level)
/usr/lib/python3.8/importlib/__init__.py:127: RemovedInSphinx40Warning: sphinx.builders.qthelp.QtHelpBuilder is deprecated. Check CHANGES for Sphinx API modifications.
  return _bootstrap._gcd_import(name[level:], package, level)
/usr/lib/python3.8/site-packages/docutils/transforms/__init__.py:171: RemovedInSphinx40Warning: An old styled index node found: <index: > at (None:None)
  transform.apply(**kwargs)