python-glyphsLib fails to build with Python 3.15.0a8.

____________________________ test_ignorable_anchors ____________________________

datadir = local('/builddir/build/BUILD/python-glyphsLib-6.13.0-build/glyphslib-6.13.0/tests/data')

    def test_ignorable_anchors(datadir):
        ufos = load_to_ufos(datadir.join("IgnorableAnchors.glyphs"))
    
        for ufo in ufos:
            writer = ContextualMarkFeatureWriter()
            feaFile = ast.FeatureFile()
            assert str(feaFile) == ""
            assert writer.write(ufo, feaFile)
    
            assert len(feaFile.markClasses) == 1
>           assert "MC_top" in feaFile.markClasses
E           AssertionError: assert 'MC_top' in {'mark_top': <fontTools.feaLib.ast.MarkClass object at 0x7fb3cf73ee90>}
E            +  where {'mark_top': <fontTools.feaLib.ast.MarkClass object at 0x7fb3cf73ee90>} = <fontTools.feaLib.ast.FeatureFile object at 0x7fb3cd2cda30>.markClasses

tests/feature_writers_test.py:74: AssertionError
___________________________ test_contextual_anchors ____________________________

datadir = local('/builddir/build/BUILD/python-glyphsLib-6.13.0-build/glyphslib-6.13.0/tests/data')

    def test_contextual_anchors(datadir):
        ufos = load_to_ufos(datadir.join("ContextualAnchors.glyphs"))
    
        for ufo in ufos:
            writer = ContextualMarkFeatureWriter()
            feaFile = ast.FeatureFile()
            assert str(feaFile) == ""
            assert writer.write(ufo, feaFile)
    
            assert len(feaFile.markClasses) == 2
>           assert "MC_bottom" in feaFile.markClasses
E           AssertionError: assert 'MC_bottom' in {'mark_bottom': <fontTools.feaLib.ast.MarkClass object at 0x7fb3cca0c3e0>, 'mark_top': <fontTools.feaLib.ast.MarkClass object at 0x7fb3cca0c510>}
E            +  where {'mark_bottom': <fontTools.feaLib.ast.MarkClass object at 0x7fb3cca0c3e0>, 'mark_top': <fontTools.feaLib.ast.MarkClass object at 0x7fb3cca0c510>} = <fontTools.feaLib.ast.FeatureFile object at 0x7fb3cc7c8ad0>.markClasses

https://docs.python.org/3.15/whatsnew/3.15.html

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.15/fedora-rawhide-x86_64/10319098-python-glyphsLib/

For all our attempts to build python-glyphsLib with Python 3.15, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.15/package/python-glyphsLib/

Testing and mass rebuild of packages is happening in copr.
You can follow these instructions to test locally in mock if your package builds with Python 3.15:
https://copr.fedorainfracloud.org/coprs/g/python/python3.15/

Let us know here if you have any questions.

Python 3.15 is planned to be included in Fedora 45.
To make that update smoother, we're building Fedora packages with all pre-releases of Python 3.15.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires),
so if this package is required a lot, it's important for us to get it fixed soon.

We'd appreciate help from the people who know this package best,
but if you don't want to work on this now, let us know so we can try to work around it on our side.