I had been using duplicity successfully to backup to GCS for some time but a few months ago it stopped working. I believe there's an encoding problem with moving to Python 3. I have seen a few similar problems floating around (e.g., https://bugs.launchpad.net/duplicity/+bug/1843995) which claim that similar bugs are resolved, but I'm still getting the following:

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/_boto_single.py", line 173, in __init__

    self.resetConnection()

  File "/usr/lib/python3/dist-packages/duplicity/backends/_boto_single.py", line 198, in resetConnection

    self.bucket = self.conn.create_bucket(self.bucket_name,

  File "/usr/lib/python3/dist-packages/boto/gs/connection.py", line 93, in create_bucket

    response = self.make_request(

  File "/usr/lib/python3/dist-packages/boto/s3/connection.py", line 659, in make_request

    auth_path = self.calling_format.build_auth_path(bucket, key)

  File "/usr/lib/python3/dist-packages/boto/s3/connection.py", line 94, in build_auth_path

    path = '/' + bucket

 TypeError: can only concatenate str (not "bytes") to str