CI: install mupif from git

.github/workflows/tests.yml

@@ -25,6 +25,7 @@ jobs:
         wget -qO - https://www.mongodb.org/static/pgp/server-5.0.asc | sudo apt-key add - && echo "deb http://repo.mongodb.org/apt/debian buster/mongodb-org/5.0 main" | sudo tee /etc/apt/sources.list.d/mongodb-org-5.0.list
         sudo apt-get update && sudo apt-get -y install python3-wheel python3-pip mongodb-org
         python -m pip install -q flake8
+        pip install git+https://github.com/mupif/mupif.git@master
         pip install -r requirements.txt
     - name: Lint with flake8
       run: |