forgot to install it

.github/workflows/test.yml

@@ -71,7 +71,7 @@ jobs:
       - name: Install Django and other Python dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install django~=${{ matrix.django-version }} coveralls xapian*.whl
+          pip install django~=${{ matrix.django-version }} filelock~=${{ matrix.filelock-version }} coveralls xapian*.whl
 
       - name: Checkout django-haystack
         uses: actions/checkout@v2