chore: set manually a working version of pip for install

[oboulant]

We recently have a problem to run the test within the CI with GH Actions.
See stackoverflow question for more detail : https://stackoverflow.com/questions/67296563/github-actions-stays-stuck-on-a-task-and-finally-fail-on-timeout

Following the comment on the stackoverflow issue, I tried in run-test.yml not to upgrade pip. It did partially the job since more runs completed. But at the end, it stayed stuck. See here to see the run.

I investigated the following message in the CI :

WARNING: Value for scheme.headers does not match. Please report this to <https://github.com/pypa/pip/issues/9617>

But it is said in the related issue that :

First off, this specific class of warnings can be safely ignored. They were added to help pip's maintainers identify incorrectly patched/configured Python distributions provided by redistributors (eg: with your OS, or as part of $corp's VM/Docker images etc).

Also in the CI trace, there is the following message :

Processing /home/runner/work/ruptures/ruptures
  DEPRECATION: A future pip version will change local packages to be built in-place without first copying to a temporary directory. We recommend you use --use-feature=in-tree-build to test your packages with this new behavior before it becomes the default.
   pip 21.3 will remove support for this functionality. You can find discussion regarding this at https://github.com/pypa/pip/issues/7555.

Related also the the use of --use-feature=in-tree-build I found this issue on pip. This very last issue has a comment that propose to do

python setup.py bdist_wheel
pip install dist/*.whl

instead of pip install . which is not a good solution for us since we are making use of the possibility to specify a [options.extras_require] like for instance python -m pip install .[test].

I also tried locally to upgrade pip to the latest version (21.1) and run python -m pip install .[test]. I had the similar problem as in the CI : the install process got stuck !! Local python version : 3.6.8.

So what I did :

• In the last working run in the CI, I looked at the pip version. It was 21.0.1. See here
• Enforce the installation of this specific version of pip

It worked locally with my 3.6.8 python version.

[codecov]

Codecov Report

Merging #153 (81214c0) into master (3d7ec0e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #153   +/-   ##
=======================================
  Coverage   96.01%   96.01%           
=======================================
  Files          40       40           
  Lines         979      979           
=======================================
  Hits          940      940           
  Misses         39       39           

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