Add installation of gettext package (required for tests)

Author: flashcode

.github/workflows/pythonpackage.yml

@@ -19,6 +19,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
+        sudo apt-get install gettext
         python -m pip install --upgrade pip
         pip install -r requirements.txt
     - name: Lint with flake8