Enforce visibility of deprecation warnings

[ghost]

Originally reported by: jaraco (Bitbucket: jaraco, GitHub: jaraco)

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With the release of 3.0, it became apparent that the DeprecationWarning for #65 wasn't adequate to raise awareness of the pending removal.

Setuptools should probably enforce visibility of DeprecationWarnings in the setuptools and pkg_resources namespaces.

Something like

warnings.filterwarnings("always", category=DeprecationWarning, module="setuptools\.|pkg_resources\.")

I'm not quite sure yet where this would happen. I'm considering it could happen at import time or possibly only during select commands initialization.

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• Bitbucket: https://bitbucket.org/pypa/setuptools/issue/159

[pganssle]

I think the way most people solve this (matplotlib, dateutil, pandas, etc) is to just not use DeprecationWarning at all. Instead, you create a subclass of Warning, like so:

class PkgResourcesDeprecationWarning(Warning):
    """Class for warning about deprecations in PkgResources"""

That way, they are on by default, but they're still easy to filter out.

[martonp]

@robinjhuang and I would like to work on this during the GA python sprint

[abravalheri]

This issue seems to be mostly solved (thanks to the various contributions), right?

(... if we ignore the situations where the build frontend hides the warnings ...)

Is there anything left to do from the setuptools point of view?