The Fix
pip install urllib3==2.4.0
Based on closed urllib3/urllib3 issue #3565 · PR/commit linked
Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.
@@ -68,6 +68,10 @@ jobs:
experimental: false
nox-session: test-pypy3.10
+ - python-version: "pypy-3.11"
+ os: ubuntu-latest
+ experimental: false
Option A — Upgrade to fixed release\npip install urllib3==2.4.0\nWhen NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.\n\n
Why This Fix Works in Production
- Trigger: [CI] PyPy tests fail because of unclosed keylogfile.txt
- Mechanism: The CI tests fail due to a ResourceWarning for an unclosed file in PyPy
- Why the fix works: Adds PyPy 3.11 to the CI matrix to address test failures related to unclosed keylogfile.txt. (first fixed release: 2.4.0).
- If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.
Why This Breaks in Prod
- The CI tests fail due to a ResourceWarning for an unclosed file in PyPy
- Production symptom (often without a traceback): [CI] PyPy tests fail because of unclosed keylogfile.txt
Proof / Evidence
- GitHub issue: #3565
- Fix PR: https://github.com/urllib3/urllib3/pull/3569
- First fixed release: 2.4.0
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.95
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.73
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“One of recent runs has been successful https://github.com/urllib3/urllib3/actions/runs/13546009736/job/37857690673”
Failure Signature (Search String)
- [CI] PyPy tests fail because of unclosed keylogfile.txt
- [PyPy CI job](https://github.com/urllib3/urllib3/actions/runs/13530170912/job/37810256991) started to fail recently because of the following warning:
Copy-friendly signature
Failure Signature
-----------------
[CI] PyPy tests fail because of unclosed keylogfile.txt
[PyPy CI job](https://github.com/urllib3/urllib3/actions/runs/13530170912/job/37810256991) started to fail recently because of the following warning:
Error Message
Signature-only (no traceback captured)
Error Message
-------------
[CI] PyPy tests fail because of unclosed keylogfile.txt
[PyPy CI job](https://github.com/urllib3/urllib3/actions/runs/13530170912/job/37810256991) started to fail recently because of the following warning:
What Broke
CI jobs fail intermittently due to unclosed file warnings, impacting test reliability.
Why It Broke
The CI tests fail due to a ResourceWarning for an unclosed file in PyPy
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install urllib3==2.4.0
Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.
Fix reference: https://github.com/urllib3/urllib3/pull/3569
First fixed release: 2.4.0
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- Do not use if it changes public behavior or if the failure cannot be reproduced.
Did This Fix Work in Your Case?
Quick signal helps us prioritize which fixes to verify and improve.
Prevention
- Add a CI check that diffs key outputs after upgrades (OpenAPI schema snapshots, JSON payload shapes, CLI output).
- Upgrade behind a canary and run integration tests against the canary before 100% rollout.
- Add a TLS smoke test that performs a real handshake in CI (include CA bundle validation and hostname checks).
- Alert on handshake failures by error string and endpoint to catch cert/CA changes quickly.
Version Compatibility Table
| Version | Status |
|---|---|
| 2.4.0 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.