duplicity run time error in 0.8.19:

('Could not unlock the acquired lock opened on `%s`',
b'/root/.cache/duplicity/apollon.dup/lockfile')
Traceback (most recent call last):
  File "/usr/lib/python3.8/site-packages/fasteners/process_lock.py", line 166,
in release
    self.unlock()
  File "/usr/lib/python3.8/site-packages/fasteners/process_lock.py", line 193,
in unlock
    self._unlock(self.lockfile)
  File "/usr/lib/python3.8/site-packages/fasteners/process_lock.py", line 430,
in _unlock
    fcntl.lockf(lockfile, fcntl.LOCK_UN)
TypeError: argument must be an int, or have a fileno() method.

This bug is fixed in duplicity 0.8.20, submitted to factory in sr#904259
Opened this bug for future reference.