Add schema to required modules

.github/workflows/pytest.yml

@@ -17,7 +17,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install flake8 discord pytest
+        pip install flake8 discord pytest schema
     - name: Analysing the code with flake8
       run: |
         flake8 --max-line-length 120 $(git ls-files '*.py')