deja-dup fails with root account

I am running deja-dup in Ubuntu 20.04 (Focal Fossa), which has duplicity/focal,now 0.8.11.1612-1 and deja-dup/focal,now 40.6-1ubuntu2.

When I run deja-dup as myself, it runs fine, but when I launch it with sudo, it fails:

Traceback (innermost last):
  File "/usr/bin/duplicity", line 106, in <module>
    with_tempdir(main)
  File "/usr/bin/duplicity", line 92, in with_tempdir
    fn()
  File "/usr/lib/python3/dist-packages/duplicity/dup_main.py", line 1525, in main
    action = commandline.ProcessCommandLine(sys.argv[1:])
  File "/usr/lib/python3/dist-packages/duplicity/commandline.py", line 1175, in ProcessCommandLine
    globals.backend = backend.get_backend(args[0])
  File "/usr/lib/python3/dist-packages/duplicity/backend.py", line 225, in get_backend
    obj = get_backend_object(url_string)
  File "/usr/lib/python3/dist-packages/duplicity/backend.py", line 211, in get_backend_object
    return factory(pu)
  File "/usr/lib/python3/dist-packages/duplicity/backends/giobackend.py", line 82, in __init__
    ensure_dbus()
  File "/usr/lib/python3/dist-packages/duplicity/backends/giobackend.py", line 37, in ensure_dbus
    output = p.communicate()[0].decode("utf8", errors="replace")
 AttributeError: 'str' object has no attribute 'decode'