The using-constant-test warning shows up on uses of things that pylint does not understand are properties when it could not inspect the decorator implementation.

Reproduction

Given the following code, run pylint (2.4.4 in my case) on it. Note the comment.

module.py

#!/usr/bin/env python3
"""Module."""

# A PyPI package - run pylint in a venv _without_ this installed!
import cached_property


class Klass:
    """Klass."""

    def __init__(self, arg):
        self.arg = arg

    def meth(self):
        if self._condition:
            print('truth')

    @cached_property.cached_property
    def _condition(self):
        return bool(self.arg)


def main():
    k = Klass(1)
    k.meth()


if __name__ == '__main__':
    main()

Assuming you follow the comment in the code and make sure you do not have cached_property installed within the environment you are running pylint in, you'll get the following in the errors:

$ pylint module.py
************* Module module
...
module.py:15:8: W0125: Using a conditional statement with a constant value (using-constant-test)
...

This is true even if you add cached_property.cached_property to your pylintrc's [BASIC] property-classes list.

It appears that property-classes is not used for the using-constant-test error check, only some other naming related ones. We should have functions or methods defined with a decorator that appears in property-classes not fail this check.

I'm not familiar enough with the code to understand where the logic that leads to a built-in property declaration working while this one does not.