optimize build

Author: tsolakoua

.github/workflows/build.yml

@@ -20,11 +20,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          python -m pip install sphinx==3.4.1
-          pip install tox==3.20.0
-          python -m pip install sphinx_rtd_theme==0.5.2
-          pip install "Jinja2<3.1"
-          pip install virtualenv
+          python -m pip install --ignore-installed sphinx==3.4.1 tox==3.20.0 sphinx_rtd_theme==0.5.2 "Jinja2<3.1" virtualenv
       - name: Test with tox
         run: |
           tox -e py