fix again sphinx version, .gitlab-ci and requirements-dev

.gitlab-ci.yml

@@ -61,7 +61,7 @@ test-centos7:
   - coverage run --source='.' manage.py test
   - coverage report
   - coverage html
-  - pip3.6 install sphinx==3.5.3 sphinx-argparse==0.2.5 sphinxcontrib.bibtex==2.1.4 sphinx_rtd_theme==0.5.1
+  - pip3.6 install sphinx==3.5.2 sphinx-argparse==0.2.5 sphinxcontrib.bibtex==2.1.4 sphinx_rtd_theme==0.5.1
   - cd docs
   - PYTHON=python3.6 make html
   artifacts:

ippisite/requirements-dev.txt

@@ -4,9 +4,9 @@ flake8
 black
 flake8-black
 # documentation generation
-sphinx
-sphinx_rtd_theme
-sphinxcontrib-bibtex
+Sphinx==3.5.2
+sphinx_rtd_theme==0.5.1
+sphinxcontrib-bibtex==2.1.4
 # coverage
 coverage
 # tests