BUILD: Readthedocs - add OS (v1.15.x)

Author: Alexey-Rivkin

.readthedocs.yaml

@@ -5,6 +5,12 @@
 # Required
 version: 2
 
+# https://docs.readthedocs.io/en/stable/config-file/v2.html#build-os
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.8"
+
 # Build documentation in the docs/ directory with Sphinx
 sphinx:
    configuration: docs/source/conf.py
@@ -14,6 +20,5 @@ sphinx:
 
 # Optionally set the version of Python and requirements required to build your docs
 python:
-   version: 3.8
    install:
-   - requirements: docs/.readthedoc.requirements.txt 
+   - requirements: docs/.readthedoc.requirements.txt