Explicitly set ubuntu-20.04 as OS and install dev dependencies

.github/workflows/docker-publish.yml

@@ -9,8 +9,8 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest]
-        python-version: [3.7, 3.8, 3.9]
+        os: [ubuntu-20.04]
+        python-version: 3.7
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}
@@ -23,10 +23,10 @@ jobs:
         sudo apt-get install -qq libpoppler-cpp-dev unpaper tesseract-ocr
     - name: Upgrade pip
       run: |
-        pip install --upgrade pip pipenv wheel sphinx pytest pytest-cov coveralls
+        pip install --upgrade pip pipenv
     - name: Gather pip requirements
       run: |
-        pipenv lock -r > requirements.txt
+        pipenv lock --dev -r > requirements.txt
     - name: Install pip requirements
       run: |
         pip install -r requirements.txt