ci: install specific version of virtualenv

Author: G-Rath

.github/workflows/ci.yml

@@ -54,6 +54,11 @@ jobs:
       - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
         with:
           python-version-file: '.python-version'
+      - # Workaround (hopefully temporary) issue with Poetry and virtualenv:
+        # - https://github.com/pypa/virtualenv/issues/2931
+        # - https://github.com/python-poetry/poetry/issues/10490
+        # - https://github.com/actions/setup-python/issues/1167
+        run: pip install virtualenv==20.32
       - run: pipx install poetry~=2.0
       - run: poetry install
       - run: poetry run mypy .
@@ -69,6 +74,11 @@ jobs:
       - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
         with:
           python-version-file: '.python-version'
+      - # Workaround (hopefully temporary) issue with Poetry and virtualenv:
+        # - https://github.com/pypa/virtualenv/issues/2931
+        # - https://github.com/python-poetry/poetry/issues/10490
+        # - https://github.com/actions/setup-python/issues/1167
+        run: pip install virtualenv==20.32
       - run: pipx install poetry~=2.0
       - run: poetry install
       - run: poetry run pytest
@@ -84,6 +94,11 @@ jobs:
       - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
         with:
           python-version-file: '.python-version'
+      - # Workaround (hopefully temporary) issue with Poetry and virtualenv:
+        # - https://github.com/pypa/virtualenv/issues/2931
+        # - https://github.com/python-poetry/poetry/issues/10490
+        # - https://github.com/actions/setup-python/issues/1167
+        run: pip install virtualenv==20.32
       - run: pipx install poetry~=2.0
       - run: poetry install
       - run: poetry run scripts/validate_advisories.py

.github/workflows/generate.yml

@@ -26,6 +26,11 @@ jobs:
       - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
         with:
           python-version-file: '.python-version'
+      - # Workaround (hopefully temporary) issue with Poetry and virtualenv:
+        # - https://github.com/pypa/virtualenv/issues/2931
+        # - https://github.com/python-poetry/poetry/issues/10490
+        # - https://github.com/actions/setup-python/issues/1167
+        run: pip install virtualenv==20.32
       - run: pipx install poetry~=2.0
       - run: poetry install
       - run: poetry run scripts/download_sa_advisories.py