def test_directoryNotPackage(self):
        """
        L{runner.filenameToModule} raises a C{ValueError} when the name of an
        empty directory is passed that isn't considered a valid Python package
        because it doesn't contain a C{__init__.py} file.
        """
        emptyDir = filepath.FilePath(self.parent).child("emptyDirectory")
        emptyDir.createDirectory()

        err = self.assertRaises(ValueError, runner.filenameToModule,
            emptyDir.path)
        self.assertEqual(str(err), "%r is not a package directory" % (
            emptyDir.path,))

        L{runner.filenameToModule} raises a C{ValueError} when the name of an
        empty directory is passed that isn't considered a valid Python package
        because it doesn't contain a C{__init__.py} file.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_loader.py