[MRG] Build POT against oldest-supported-numpy (local PR)

[rflamary]

Types of changes

this PR is a local (branch) version of #347 that will actually run the wheel building.

Motivation and context / Related issue

Fixes #346

How has this been tested (if it applies)

PR checklist

• I have read the CONTRIBUTING document.
• The documentation is up-to-date with the changes I made (check build artifacts).
• All tests passed, and additional code has been covered with new tests.
• I have added the PR and Issue fix to the RELEASES.md file.

[codecov]

Codecov Report

Merging #349 (aac1a2a) into master (50c0f17) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #349      +/-   ##
==========================================
- Coverage   93.63%   93.59%   -0.04%     
==========================================
  Files          22       22              
  Lines        5591     5591              
==========================================
- Hits         5235     5233       -2     
- Misses        356      358       +2     

[davidghiurco]

Adding suggestions to reconcile build restrictions with python_requires=">=3.6" in setup.py

[davidghiurco]

@rflamary I noticed you might want to apply the changes made in build_wheels.yml to build_wheels_weekly.yml: https://github.com/PythonOT/POT/blob/master/.github/workflows/build_wheels_weekly.yml#L42-L43

[davidghiurco]

And if you do apply those changes, you might want to add to release notes that Python 3.6 support is back.

[rflamary]

We are not adding python3.6 support back because python 3.6 is not supported and we should not promote old unsupported code. Actually the wheels are not builded for 3.6 because it is not supported anymore and the CI does not test 3.6. We are just allowing the user to install it even if it is not supported.

I'll update the weekly the wheels in an other PR.