github: use virtual environment

.github/workflows/tests.yaml

@@ -33,14 +33,18 @@ jobs:
           path: .venv
       - name: Install system packages
         run: sudo apt-get install -y portaudio19-dev
-      - name: Install basic dependencies
+      - name: Setup virtual environment
+        run: |
+          python -m venv .venv
+          source .venv/bin/activate
+      - name: Install basic Python dependencies
         run: |
           python -m pip install --upgrade pip
           pip install -r requirements.txt
       - name: Build project
         run: |
           python -m build
-      - name: Install project and other dependencies
+      - name: Install project and other Python dependencies
         run: |
           pip install --editable .
       - name: Test with pytest