Error "No module named pip" with Python2.7

[cas--]

Checklist

• I added a descriptive title
• I searched open reports and couldn't find a duplicate

What happened?

We have a legacy system that is still running Python2 and the CI build system recently started failing due to the following error when it picked up a new docker image with Conda 23.10.

Pip subprocess error:

/opt/conda/envs/national/bin/python: No module named pip

Installing pip dependencies: ...working... Ran pip subprocess with arguments:

['/opt/conda/envs/national/bin/python', '-m', 'pip', 'install', '-U', '-r', '/opt/atlassian/pipelines/agent/build/condaenv.3ycmalfz.requirements.txt', '--exists-action=b']

Pip subprocess output:

failed

CondaEnvException: Pip failed

We can replicate with a minimal test.yml

channels:
  - conda-forge
dependencies:
  - python=2.7.18
  - pip
  - pip:
    - boto3

and Dockerfile:

FROM continuumio/miniconda3:latest
# works: 23.9.0-0
# broken: 24.1.2-0 23.10.0-1

COPY test.yml .

RUN set -ex && \
    conda env create --name test --file test.yml

I then noticed in the release notes for Conda 23.10 that this solver was now default so testing again with classic solver there was no issue.

-     conda env create --name test --file test.yml
+     conda env create --solver=classic --name test --file test.yml

I didn't see anything specifically mentioning that this solver does not support Python2

Conda Info

No response

Conda Config

No response

Conda list

No response

Additional Context

No response

[cas--]

I think i have identified the root of the issue, it seems that Python 2.7.18 is not available in conda-forge, latest is 2.7.15.

• https://anaconda.org/conda-forge/python/files?version=2.7.15
• https://anaconda.org/conda-forge/python/files?version=2.7.18
• https://anaconda.org/anaconda/python/files?version=2.7.18

So modifying the test.yml to use the older version on conda forge now works:

channels:
  - conda-forge
dependencies:
  - python=2.7.15
  - pip
  - pip:
    - boto3

Not sure what this means for this bug status and whether this should be closed 🤔

[jaimergp]

That's odd. Do you have earlier output for the original error? If the env failed to solve, it should have failed before running pip 🤔

[cas--]

Here is the full error.log with increased verbosity but it does not show any issues.

I did however find in the Mamba docs troubleshooting guide to not mix channels which I would assume applies here

Using the default and conda-forge channels at the same time is not supported and will lead to broken environments:

Although it might be useful if libmamba generated a log warning when it encounters this scenario.

[jaimergp]

You are asking for 2.7.18 but conda-forge only has up to 2.7.15, hence the solver is forced to pick from defaults, which creates the incompatibility I'd guess.

Try to use only defaults, or only conda-forge, or pick python=2.7 so the solver has some more leeway.