.readthedocs.yml: specify some minimum python requirements

# .readthedocs.yml

# Read the Docs configuration file

# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details

# Required

version: 2

# Build documentation in the docs/ directory with Sphinx

sphinx:

  configuration: docs/conf.py

# We want all the document formats

formats: all

# For consistency, we require that QEMU's Sphinx extensions

# run with at least the same minimum version of Python that

# we require for other Python in our codebase (our conf.py

# enforces this, and some code needs it.)

python:

  version: 3.5