How to use the pathlib2.PosixPath function in pathlib2

return os.path.join(BASE, *x)


def rel_join(*x):
    return os.path.join(TESTFN, *x)


only_nt = unittest.skipIf(os.name != 'nt',
                          'test requires a Windows-compatible system')
only_posix = unittest.skipIf(os.name == 'nt',
                             'test requires a POSIX-compatible system')


@only_posix
class PosixPathAsPureTest(PurePosixPathTest):
    cls = pathlib.PosixPath


@only_nt
class WindowsPathAsPureTest(PureWindowsPathTest):
    cls = pathlib.WindowsPath

    def test_owner(self):
        P = self.cls
        with self.assertRaises(NotImplementedError):
            P('c:/').owner()

    def test_group(self):
        P = self.cls
        with self.assertRaises(NotImplementedError):
            P('c:/').group()

def test_unsupported_flavour(self):
        if os.name == 'nt':
            self.assertRaises(NotImplementedError, pathlib.PosixPath)
        else:
            self.assertRaises(NotImplementedError, pathlib.WindowsPath)