Why do I need long_description_content_type='text/markdown' ?

[Allan-CodeWorks]

Hello there!

I replaced login/password by trusted publishing on the repo I maintain.
One thing surprises me but I can't find explaination, i had to add long_description_content_type='text/markdown', in my setup.py otherwise publishing would get me the following :

ERROR    `long_description` has syntax errors in markup and would not be        
         rendered on PyPI.                                                      
         No content rendered from RST source.                                   
WARNING  `long_description_content_type` missing. defaulting to `text/x-rst`.   
Checking dist/OpenFisca-France-Local-Francis-6.11.4.tar.gz: PASSED with warnings
WARNING  `long_description_content_type` missing. defaulting to `text/x-rst`.   
WARNING  `long_description` missing.                                            

The actual workflow is accessible : here

We did not use the long_description field and we still don´t so why does it fails / forces me to add this?
Can I avoid adding this to the setup?

Thanks for your time!

[webknjaz]

That's what twine check --strict requires. Some of the reported problems are warnings, others may be errors that would cause PyPI to reject uploads.
In this action, you can disable the metadata validation and live dangerously. See the readme.

N.B. Twine validates the metadata of the resulting package distributions, that can be created by different build backends, in an agnostic manner. In your case, it's setuptools, so take it up with them how the metadata is created. This action doesn't build the dists.

[Allan-CodeWorks]

Thank you very much for answering, this makes things clearer!