build: Update pipeline to use poetry

Author: dclimber

.github/workflows/pytest.yml

@@ -32,11 +32,14 @@ jobs:
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v2
       with:
-        python-version:  ${{ matrix.python-version }}
+        python-version: ${{ matrix.python-version }}
+    - name: Install poetry
+      uses: snok/install-poetry@v1
+      with:
+        virtualenvs-create: true
+        virtualenvs-in-project: true
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        pip install -r tests/dev.requirements.txt
+      run: poetry install --no-interaction --no-root
     - name: Test with pytest
       env:
         POSTGRES_DB: test
@@ -45,4 +48,5 @@ jobs:
         POSTGRES_HOST: localhost
         POSTGRES_PORT: ${{ job.services.postgres.ports[5432] }}
       run: |
+        source .venv/bin/activate
         pytest