The bin/install script from swh-environment has been updated to install
swh dependencies in a same manner as in the build script so we can now
use it.
Also workaround pip regression (https://github.com/pypa/pip/issues/10573)
by using the --no-use-pep517 option.
Also workaround pip regression (https://github.com/pypa/pip/issues/10573)
by temporarily pinning its version to <21.3.
I hacked on the jenkins job to test the changes and it is working again,
see https://jenkins.softwareheritage.org/job/DENV/job/tests/1670/console.
Related to T3663