Revert "Remove all caching that could explain the problem"

This reverts commit 7e6684b.

Author: Pierre-Sassoulas

.github/workflows/main.yml

@@ -13,6 +13,8 @@ jobs:
       - uses: actions/checkout@v4
       - name: Set up Python
         uses: actions/setup-python@v5
+        with:
+          cache: "pip"
       - name: Install pypa/build
         run: >-
           python3 -m pip install --user --upgrade build twine pkginfo poetry
@@ -72,7 +74,15 @@ jobs:
         run: |
           python -m poetry config virtualenvs.in-project true
 
+      - name: Cache the virtualenv
+        id: poetry-dependencies-cache
+        uses: actions/cache@v3
+        with:
+          path: ./.venv
+          key: ${{ runner.os }}-venv-${{ steps.setup-python.outputs.python-version }}-${{ hashFiles('**/poetry.lock') }}
+
       - name: Install dev dependencies
+        if: steps.poetry-dependencies-cache.outputs.cache-hit != 'true'
         run: |
           python -m poetry install --only=dev