def test_mountpoint_error(self):
        mountroot = mountroot_for_test(self)
        intermediate = mountroot.child(b"mount-error-test")
        intermediate.setContent(b"collision")
        mountpoint = intermediate.child(b"mount-test")
        _, mount_result = self._run_test(mountpoint)

        failure = self.failureResultOf(mount_result, OSError)
        self.assertEqual(ENOTDIR, failure.value.errno)
If the mountpoint is unusable, for example because it is a regular file
dataset/ETHPy150Open ClusterHQ/flocker/flocker/node/agents/test/test_blockdevice.py/MountBlockDeviceTests.test_mountpoint_error