I quickly hacked on Jenkins job to remove the pip upgrade but the default pip version on the docker image is too outdated
and some swh dependencies will fail to install, see console output.

So I guess we will have to pin pip to < 21.3 to fix the issue.

I pushed D6484 to fix the build issue. Instead of pinning pip version, I used the --no-use-pep517 pip option as suggested in the pip github issue.

Argh ...

09:13:54 Collecting tree-sitter
09:13:54   Using cached tree_sitter-0.19.0.tar.gz (112 kB)
09:13:54 ERROR: Disabling PEP 517 processing is invalid: project specifies a build backend of setuptools.build_meta in pyproject.toml

Looks like pinning pip is the only solution here at the end.