urllib3 Cannot run tests on Ubuntu 14.04 LTS + Python 3

The Fix

pip install urllib3==1.25

Based on closed urllib3/urllib3 issue #822 · 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%.

Jump to Verify Open PR/Commit

@@ -192,6 +192,7 @@ In chronological order:
 * Jesse Shapiro <[email protected]>
   * Working on encoding unicode header parameter names
+  * Making setup.py resilient to ASCII locales
 
 * [Your name or handle] <[email or website]>

repro.py

# (Install Docker from: http://www.docker.com )

# If OS X, start with:
$ docker-machine start default; eval "$(docker-machine env default)"

# If OS X or Linux, continue with:
$ docker run -it ubuntu:trusty  # Ubuntu 14.04 LTS
$$ apt-get update
$$ apt-get install git -y
$$ apt-get install python3-pip -y
$$ pip3 install virtualenv
$$ git clone https://github.com/shazow/urllib3
$$ cd urllib3/
$$ virtualenv venv
$$ source venv/bin/activate
$$ make test

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

fix.md

Option A — Upgrade to fixed release\npip install urllib3==1.25\nWhen NOT to use: This fix is not suitable for environments where ASCII-only files are guaranteed.\n\n

Why This Fix Works in Production

Trigger: python setup.py develop
Mechanism: Fixes the setup.py to support ASCII locales by using codecs to read files with UTF-8 encoding.
Why the fix works: Fixes the setup.py to support ASCII locales by using codecs to read files with UTF-8 encoding. (first fixed release: 1.25).

Production impact:

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

Shows up under Python 3.4 in real deployments (not just unit tests).
Surfaces as: python setup.py develop

Proof / Evidence

GitHub issue: #822
Fix PR: https://github.com/urllib3/urllib3/pull/823
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: 0.41

Discussion

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

Jump to Sources Open on GitHub

“Likely fix that works on Python 2 and 3: io.open('README.rst', encoding='utf8')”

@davidfstr · 2016-03-22 · source

“Oh you support Python 2.6 too. Here's a more-compatible version: codecs.open('README.rst', encoding='utf8')”

@davidfstr · 2016-03-22 · source

“Hm strange, can't reproduce the error on Python 3.5. Does changing it to u'\n\n' help at all?”

@shazow · 2016-03-22 · source

“This is _almost certainly_ a locale problem”

@Lukasa · 2016-03-22 · source

Failure Signature (Search String)

python setup.py develop

Error Message

Stack trace

error.txt

Error Message
-------------
python setup.py develop
Traceback (most recent call last):
  File "setup.py", line 23, in <module>
    long_description=open('README.rst').read() + '\n\n' + open('CHANGES.rst').read(),
  File "/urllib3/venv/lib/python3.4/encodings/ascii.py", line 26, in decode
    return codecs.ascii_decode(input, self.errors)[0]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xf0 in position 4597: ordinal not in range(128)
make: *** [*.egg-info] Error 1

Minimal Reproduction

repro.py

# (Install Docker from: http://www.docker.com )

# If OS X, start with:
$ docker-machine start default; eval "$(docker-machine env default)"

# If OS X or Linux, continue with:
$ docker run -it ubuntu:trusty  # Ubuntu 14.04 LTS
$$ apt-get update
$$ apt-get install git -y
$$ apt-get install python3-pip -y
$$ pip3 install virtualenv
$$ git clone https://github.com/shazow/urllib3
$$ cd urllib3/
$$ virtualenv venv
$$ source venv/bin/activate
$$ make test

Environment

Python: 3.4

Fix Options (Details)

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

pip install urllib3==1.25

When NOT to use: This fix is not suitable for environments where ASCII-only files are guaranteed.

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/823

First fixed release: 1.25

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

When NOT to Use This Fix

This fix is not suitable for environments where ASCII-only files are guaranteed.

Verify Fix

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

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:configuration-error urllib3 hub urllib3 best practices All hubs All clusters

Related clusters: Data consistency SSL handshake Other

Sources

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

urllib3 Cannot run tests on Ubuntu 14.04 LTS + Python 3 (Fix)