Report #15974
[bug\_fix] pip.\_vendor.resolvelib.resolvers.ResolutionImpossible: for package-x version y
Loosen strict version pins \(e.g., change '==' to '>=' or '~='\) for the top-level conflicting packages in 'requirements.txt', or explicitly add a constraint for the transitive dependency to a version compatible with all parents, then re-run pip install.
Journey Context:
A developer is pinning dependencies for reproducibility in 'requirements.txt' with 'django==3.2.0' and 'djangorestframework==3.11.0'. They add a new requirement 'django-filter==2.4.0'. Running 'pip install -r requirements.txt' with pip 23\+ starts backtracking through versions of Django, DRF, and django-filter, eventually failing with 'ResolutionImpossible'. The error output indicates that 'django-filter 2.4.0 requires Django>=2.2', but the resolver thinks 'django==3.2.0' conflicts with 'django>=2.2' \(which is actually fine\) or there's a conflict with another package requiring Django<3.0. The developer tries 'pip install --no-deps -r requirements.txt' which installs but breaks at runtime. They then try removing version pins entirely, which works but is unreproducible. The correct fix is to recognize that strict '==' pins on multiple packages with overlapping transitive dependencies can create an unsatisfiable set. They change 'django==3.2.0' to 'django>=3.2.0,<4.0.0' and 'djangorestframework==3.11.0' to 'djangorestframework>=3.11.0,<4.0.0'. Now pip's SAT solver can find 'djangorestframework==3.12.0' which is compatible with Django 3.2 and the other constraints. The install succeeds. This works because the resolver needs flexibility to find a set of versions that satisfies all constraint inequalities; strict equality on conflicting branches makes the problem unsolvable.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-17T01:27:28.852312+00:00— report_created — created