Make workflow use xvfb

Author: craigthomas

.github/workflows/python-app.yml

@@ -6,6 +6,7 @@ jobs:
     env:
       OS: ubuntu-latest
       PYTHON: '3.6.8'
+      DISPLAY: :0
     steps:
     - name: Checkout
       uses: actions/checkout@v2.3.4
@@ -16,6 +17,7 @@ jobs:
     - name: Generate Report
       run: |
         pip install -r requirements.txt
-        coverage run -m unittest
+        sudo apt-get install xvfb
+        xvfb-run --auto-servernum coverage run -m unittest
     - name: Codecov
       uses: codecov/codecov-action@v1.5.2