CI: Builds are failing due to pip._vendor.resolvelib.resolvers.InconsistentCandidate error

[csadorf]

The automated builds for readthedocs.org on PRs are currently failing (example) with:

pip._vendor.resolvelib.resolvers.InconsistentCandidate: Provided candidate AlreadyInstalledCandidate(requests 2.27.1 (/home/docs/checkouts/readthedocs.org/user_builds/aiidalab-widgets-base/envs/274/lib/python3.7/site-packages)) does not satisfy SpecifierRequirement('requests~=2.26'), SpecifierRequirement('requests~=2.26.0'), SpecifierRequirement('requests'), SpecifierRequirement('requests>=2.5.0'), SpecifierRequirement('requests'), SpecifierRequirement('requests'), SpecifierRequirement('requests~=2.26')

The issue is an inconsistent specification of the requests library version. I am currently investigating the cause.

[csadorf]

The RTD dependencies introduce the requests>=2.0.0 dependencies via sphinx and sphinx-rtd-theme which currently install requests==2.27.0 into the environment. Then pip install --upgrade --upgrade-strategy eager --no-cache-dir .[docs] fails, because of the requests~=2.26 dependency via aiidalab. Those two dependencies are compatible, so it is unclear why setuptools throughs the InconsistentCandidate error.

[csadorf]

It could be related to issues pypa/pip#9613 and pypa/packaging#421 .

[csadorf]

Pip is vendoring packaging==21.0 which does not yet contain the fix for pypa/packaging#421 .

[csadorf]

The aiidalab package actually requires requests~=2.26.0 which indeed conflicts with requests==2.27.0. Pipdeptree incorrectly reported the dependency as requests~=2.26 which is likely also due to pypa/packaging#421 .