urllib3 Address flaky macOS tests (Fix)

The Fix

pip install urllib3==1.25

Based on closed urllib3/urllib3 issue #1372 · PR/commit linked

Open PR/Commit

@@ -1,869 +0,0 @@
@@ -1,869 +0,0 @@
-from __future__ import with_statement
-import errno
-import os

fix.md

Option A — Upgrade to fixed release\npip install urllib3==1.25\nWhen NOT to use: Do not apply this fix if the underlying issue with client cert support is resolved.\n\n

Why This Fix Works in Production

Trigger: Flaky tests on macOS causing CI failures and unreliable test results.
Mechanism: Intermittent permission denied error when creating a keychain for client certs on macOS
Why the fix works: Address flaky macOS tests by allowing certain tests to fail on macOS. (first fixed release: 1.25).

Why This Breaks in Prod

Intermittent permission denied error when creating a keychain for client certs on macOS
Production symptom (often without a traceback): Flaky tests on macOS causing CI failures and unreliable test results.

Proof / Evidence

GitHub issue: #1372
Fix PR: https://github.com/urllib3/urllib3/pull/1358
First fixed release: 1.25
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.84

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“I am submitting a PR that will patch the tests to not fail for now. The underlying issue is still there. These two tests fail…”

@crwilcox · 2018-04-20 · source

“@SethMichaelLarson , did your fix take hold for this? I think this can be closed now.”

@crwilcox · 2018-05-13 · source

“I think so! There's still one flaky macOS socket level test but it's unrelated to my issue. I'll close for now!”

@sethmlarson · 2018-05-13 · source

Failure Signature (Search String)

Flaky tests on macOS causing CI failures and unreliable test results.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Flaky tests on macOS causing CI failures and unreliable test results.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Flaky tests on macOS causing CI failures and unreliable test results.

What Broke

Flaky tests on macOS causing CI failures and unreliable test results.

Why It Broke

Intermittent permission denied error when creating a keychain for client certs on macOS

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install urllib3==1.25

When NOT to use: Do not apply this fix if the underlying issue with client cert support is resolved.

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/1358

First fixed release: 1.25

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

Do not apply this fix if the underlying issue with client cert support is resolved.

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.

Version Compatibility Table

Version	Status
1.25	Fixed

Related Issues

No related fixes found.

Cluster: urllib3:auth urllib3 hub urllib3 best practices All hubs All clusters

Related clusters: Configuration error Data consistency SSL handshake

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.