Cannot build man page on 2.1.0

[lgbaldoni]

Minor problem:

> make man
sphinx-build -b man -d _build/doctrees  -n -W . _build/man
Running Sphinx v2.3.1

Warning, treated as error:
html_static_path entry '_static' does not exist
make: *** [Makefile:141: man] Error 2

Major problem:

> make man
sphinx-build -b man -d _build/doctrees  -n -W . _build/man
Running Sphinx v2.3.1
/usr/lib/python3.8/site-packages/sphinx/events.py:103: RemovedInSphinx30Warning: autodoc_default_flags is now deprecated. Please use autodoc_default_options instead.
  results.append(callback(self.app, *args))
loading intersphinx inventory from http://docs.python.org/3.5/objects.inv...
loading intersphinx inventory from http://guessit.readthedocs.org/en/latest/objects.inv...
loading intersphinx inventory from http://babelfish.readthedocs.org/en/latest/objects.inv...
loading intersphinx inventory from http://dogpilecache.readthedocs.org/en/latest/objects.inv...
loading intersphinx inventory from http://dogpilecore.readthedocs.org/en/latest/objects.inv...
intersphinx inventory has moved: http://docs.python.org/3.5/objects.inv -> https://docs.python.org/3.5/objects.inv
intersphinx inventory has moved: http://babelfish.readthedocs.org/en/latest/objects.inv -> https://babelfish.readthedocs.io/en/latest/objects.inv
loading intersphinx inventory from http://docs.openstack.org/developer/stevedore/objects.inv...
intersphinx inventory has moved: http://guessit.readthedocs.org/en/latest/objects.inv -> https://guessit.readthedocs.io/en/latest/objects.inv
loading intersphinx inventory from http://click.pocoo.org/4/objects.inv...
loading intersphinx inventory from http://rarfile.readthedocs.org/en/latest/objects.inv...
intersphinx inventory has moved: http://click.pocoo.org/4/objects.inv -> https://click.palletsprojects.com/en/4.x/objects.inv
intersphinx inventory has moved: http://rarfile.readthedocs.org/en/latest/objects.inv -> https://rarfile.readthedocs.io/en/latest/objects.inv
intersphinx inventory has moved: http://dogpilecache.readthedocs.org/en/latest/objects.inv -> https://dogpilecache.sqlalchemy.org/en/latest/objects.inv
intersphinx inventory has moved: http://docs.openstack.org/developer/stevedore/objects.inv -> https://docs.openstack.org/stevedore/latest/

Warning, treated as error:
failed to reach any of the inventories with the following issues:
intersphinx inventory 'http://dogpilecore.readthedocs.org/en/latest/objects.inv' not fetchable due to <class 'requests.exceptions.HTTPError'>: 404 Client Error: Not Found for url: https://dogpilecore.readthedocs.io/en/latest/objects.inv
make: *** [Makefile:141: man] Error 2

[getzze]

this is fixes on main.