set up poetry install for docs

.readthedocs.yaml

@@ -10,10 +10,15 @@ build:
   os: ubuntu-20.04
   tools:
     python: "3.9"
-    # You can also specify other tool versions:
-    # nodejs: "16"
-    # rust: "1.55"
-    # golang: "1.17"
+  jobs:
+    post_create_environment:
+      # Install poetry
+      # https://python-poetry.org/docs/#osx--linux--bashonwindows-install-instructions
+      - curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python -
+      # Tell poetry to not use a virtual environment
+      - $HOME/.poetry/bin/poetry config virtualenvs.create false
+      # Install project's dependencies
+      - $HOME/.poetry/bin/poetry install
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx:
@@ -26,6 +31,5 @@ sphinx:
 # Optionally declare the Python requirements required to build your docs
 python:
    install:
-   - requirements: requirements.txt
-   - method: setuptools
+   - method: pip
      path: .