Comment 1 for bug 1853655

The traceback says you are running Python 3.7, not 2.7. Plus, it looks to be from an older version of duplicity. Please uninstall all versions of duplicity, especially those from the repo, then reinstall from one of the ones below. "sudo apt uninstall duplicity"

Do a 'which -a duplicity' to find if multiple versions are installed. Remove all. Look in /usr/lib64/pythonX.Y/site packages and remove any duplicity directory found.

* Release tarball Install - https://launchpad.net/duplicity/+download
* Daily duplicity builds - https://launchpad.net/~duplicity-team/+archive/ubuntu/daily-dev-trunk
* Stable snap builds - “sudo snap install duplicity —classic"