Poetry enforce specific Python version (#173)

* Simplify poetry using correct python version

* Make sure that exactly same Python version is used as for poetry

* Set same Python version enforcement for lint job as well

* Do for all related workflows

* Update python_docs_check.yaml

* Add comment explaining the change

.github/workflows/python_integration_tests.yaml

@@ -80,6 +80,10 @@ jobs:
       - name: Install Python dependencies
         run: |
           pipx install --python ${{ matrix.python-version }} poetry
+          # This forces poetry to use specific Python version when installing a project.
+          # Raises error, if this Python version does not match project specific Python constraints. 
+          poetry config virtualenvs.use-poetry-python true
+          poetry env use ${{ matrix.python-version }}
           make install-dev
 
       - name: Run integration tests

.github/workflows/python_lint_check.yaml

@@ -23,6 +23,10 @@ jobs:
       - name: Install Python dependencies
         run: |
           pipx install --python ${{ matrix.python-version }} poetry
+          # This forces poetry to use specific Python version when installing a project.
+          # Raises error, if this Python version does not match project specific Python constraints. 
+          poetry config virtualenvs.use-poetry-python true
+          poetry env use ${{ matrix.python-version }}
           make install-dev
 
       - name: Run lint check

.github/workflows/python_type_check.yaml

@@ -23,6 +23,10 @@ jobs:
       - name: Install Python dependencies
         run: |
           pipx install --python ${{ matrix.python-version }} poetry
+          # This forces poetry to use specific Python version when installing a project.
+          # Raises error, if this Python version does not match project specific Python constraints. 
+          poetry config virtualenvs.use-poetry-python true
+          poetry env use ${{ matrix.python-version }}
           make install-dev
 
       - name: Run type check

.github/workflows/python_unit_tests.yaml

@@ -32,38 +32,13 @@ jobs:
         run: |
           pip install poetry
 
-      - name: Check Python version against project requirements
-        shell: python
-        run: |
-          import sys
-          from contextlib import suppress
-          from poetry.core.constraints.version import parse_constraint
-
-          try:
-            import tomllib
-          except ImportError:
-            import tomli as tomllib
-
-          config = tomllib.load(open('pyproject.toml', 'rb'))
-          constraints = []
-
-          with suppress(KeyError):
-            constraints.append(parse_constraint(config['tool']['poetry']['dependencies']['python']))
-          with suppress(KeyError):
-            constraints.append(parse_constraint(config['project']['requires-python']))
-
-          python_version = parse_constraint('${{ matrix.python-version }}')
-          if not all(con.allows(python_version) for con in constraints):
-            print(f'Python version {str(python_version)} is not allowed by project settings', file=sys.stderr)
-            sys.exit(1)
-
-      - name: Uninstall global poetry again
-        run: |
-          pip uninstall -y poetry
-
       - name: Install Python dependencies
         run: |
           pipx install --python ${{ matrix.python-version }} poetry
+          # This forces poetry to use specific Python version when installing a project.
+          # Raises error, if this Python version does not match project specific Python constraints.
+          poetry config virtualenvs.use-poetry-python true
+          poetry env use ${{ matrix.python-version }}
           make install-dev
 
       - name: Run unit tests