docs: Support building documentation locally
docs: Support building documentation locally

Building the documentation locally without Internet access will fail,
because sphinx will try to download the intersphinx inventory from
http://docs.python.org/3/objects.inv.

Support building the documentation locally without Internet access by
searching for locally installed intersphinx inventory first.

Bug-Debian: https://bugs.debian.org/755026
Signed-off-by: Benjamin Drung <86a6db991ec5c1a96f98c92b98df9d547d7c8c84@ionos.com>

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt