requirements: Workaround ImportError when running pytest
markupsafe 2.1.0 removes functions that were used by Jinja2 < 3, the latter being a dependency of pybadges.
As Jinja2 < 3 is installed in the venv, pinning markupsafe to a version still compatible with Jinja2 < 3 is the only way to avoid error when running pytest as some plugins import jinja2.
See https://jenkins.softwareheritage.org/job/DENV/job/tests/2187/ and https://jenkins.softwareheritage.org/blue/organizations/jenkins/DWAPPS%2Ftests/detail/tests/2829/pipeline
Migrated from D7205 (view on Phabricator)