install pytest-asyncio in CI

Author: FlorianLudwig

.github/workflows/python-package.yml

@@ -26,7 +26,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        python -m pip install flake8 pytest
+        python -m pip install flake8 pytest pytest-asyncio
         python -m pip install .
     - name: Lint with flake8
       run: |