Fix sphinx installation in GitHub Actions (#953)

.github/workflows/unit_tests.yml

@@ -43,6 +43,10 @@ jobs:
  python-version: ${{ matrix.python-version }}
  cache: 'pip'
 
+ - name: install dependencies
+ run: |
+ pip install ".[test]"
+
  - name: install sphinx from PyPI or from git
  run: |
  if echo "${{ matrix.sphinx-version }}"|grep -q git; then
@@ -51,9 +55,5 @@ jobs:
  pip install -Iv Sphinx==${{ matrix.sphinx-version }}
  fi
 
- - name: install dependencies
- run: |
- pip install ".[test]"
-
  - name: run the unit tests
  run: make dev-test