"Package would be ignored" Error on building

[bassmadrigal]

I'm the cppy package maintainer for SlackBuilds.org (official 3rd-party repo for Slackware Linux). I just realized my version was out-of-date, so I updated the SlackBuild for PEP517. The program builds ok and the resulting package doesn't seem to cause any problems (importing it works fine), however I received the error below.

Ultimately, I want to validate whether this is just noise that can be ignored at a packaging level or if this could cause issues on a system that has this package installed before I push this update to the repo?

Thanks!

/opt/python3.9/site-packages/setuptools/command/build_py.py:212: _Warning: Package 'cppy.include.cppy' is absent from the `packages` configuration.
!!

        ********************************************************************************
        ############################
        # Package would be ignored #
        ############################
        Python recognizes 'cppy.include.cppy' as an importable package[^1],
        but it is absent from setuptools' `packages` configuration.

        This leads to an ambiguous overall configuration. If you want to distribute this
        package, please make sure that 'cppy.include.cppy' is explicitly added
        to the `packages` configuration field.

        Alternatively, you can also rely on setuptools' discovery methods
        (for example by using `find_namespace_packages(...)`/`find_namespace:`
        instead of `find_packages(...)`/`find:`).

        You can read more about "package discovery" on setuptools documentation page:

        - https://setuptools.pypa.io/en/latest/userguide/package_discovery.html

        If you don't want 'cppy.include.cppy' to be distributed and are
        already explicitly excluding 'cppy.include.cppy' via
        `find_namespace_packages(...)/find_namespace` or `find_packages(...)/find`,
        you can try to use `exclude_package_data`, or `include-package-data=False` in
        combination with a more fine grained `package-data` configuration.

        You can read more about "package data files" on setuptools documentation page:

        - https://setuptools.pypa.io/en/latest/userguide/datafiles.html


        [^1]: For Python, any directory (with suitable naming) can be imported,
              even if it does not contain any `.py` files.
              On the other hand, currently there is no concept of package data
              directory, all directories are treated like packages.
        ********************************************************************************

!!