pipenv "Locking Failed!" dependency resolution in CI

pipenv ran its resolver over your Pipfile and could not find versions that satisfy every requirement. It prints "Locking Failed!" with the offending dependency and constraint.

What this error means

pipenv lock or pipenv install fails with "Locking Failed!" and a resolver trace naming the package whose constraints could not be satisfied.

python

Locking Failed!
ResolutionImpossible:
[('urllib3<2', ...), ('urllib3>=2', ...)]

Common causes

Incompatible constraints in the Pipfile

Two requirements demand non-overlapping ranges of a shared dependency, so pipenv cannot lock a single version.

A package unavailable for the target Python

A pinned package has no release for the Pipfile's python_version, so resolution fails.

How to fix it

Resolve the conflicting constraint

Read which package pipenv could not lock.
Loosen the over-tight constraint or upgrade the capping dependency in the Pipfile.
Re-run pipenv lock and commit the new Pipfile.lock.

Terminal

pipenv lock --clear

Align python_version with available wheels

Set the Pipfile Python to a version your dependencies support so a lock is feasible.

Pipfile

[requires]
python_version = "3.12"

How to prevent it

Keep Pipfile constraints as ranges where possible.
Run pipenv lock before pushing so failures surface locally.
Match python_version to the wheels your dependencies publish.