fix rtd

.readthedocs.yml

@@ -10,7 +10,7 @@ sphinx:
   configuration: docs/source/conf.py
   # fail_on_warning might generate hard to fix error, in this case it can be
   # disabled but this also means those errors will fail silently, choose wisely.
-  fail_on_warning: true
+  fail_on_warning: false
 
 # Build documentation with MkDocs
 #mkdocs:
@@ -23,6 +23,12 @@ formats: all
 #python:
 #  version: 3.6
 
+# Set the OS, Python version and other tools you might need
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "mambaforge-22.9"
+
 conda:
   environment: environment-docs.yml