Fix docs build (#252)

Author: gjoseph92

.pdm-python

@@ -9,9 +9,15 @@ build:
     python: "3.8"
   jobs:
     post_install:
+      - env
+      - ls -al $READTHEDOCS_VIRTUALENV_PATH
+      - python --version
+      - python -c "import sys; print(sys.executable)"
+      - ls -l $(python -c "import sys; print(sys.executable)")
       # Install PDM in its own isolated environment, so docs deps don't trample its deps
-      - curl -sSL https://raw.githubusercontent.com/pdm-project/pdm/main/install-pdm.py | python3 -
+      - curl -sSL https://raw.githubusercontent.com/pdm-project/pdm/main/install-pdm.py | python -
       # TODO how to get `pdm` on the $PATH?
+      - VIRTUAL_ENV=$READTHEDOCS_VIRTUALENV_PATH $HOME/.local/bin/pdm info
       # https://github.com/pdm-project/pdm/discussions/1365#discussioncomment-3581356
       # NOTE: pandoc fails in isolation mode
-      - VIRTUAL_ENV=$(dirname $(dirname $(which python))) $HOME/.local/bin/pdm sync --no-isolation -G viz -dG docs
+      - VIRTUAL_ENV=$READTHEDOCS_VIRTUALENV_PATH $HOME/.local/bin/pdm sync -v -G viz -dG docs