setup: support Bleach 4.2 for Python 3.10 support Changelog shows no significant API changes. Bleach 3.2 and later are however even more unreasonably paranoid than 3.1, and the test thus has to be updated and we stop supporting 3.1 .

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
.