Backup to S3 not possible due to Python3 decoding error

*Setup*

Deja-Dup 40.1 (Snap revision 182)
Duplicity 0.8.00
Ubuntu 18.04

*How to reproduce*

Attempt a (encrypted) backup via `deja-dup --backup` to S3. Observe the following output:

*Actual output* (by specifying DEJA_DUP_DEBUG=1)

On GUI: "Giving up after 5 attempts. TypeError: must be str, not bytes"

DEBUG output:
---
Backtrace of previous error: Traceback (innermost last):
DUPLICITY: . File "/snap/deja-dup/182/lib/python3.6/site-packages/duplicity/backend.py", line 374, in inner_retry
DUPLICITY: . return fn(self, *args)
DUPLICITY: . File "/snap/deja-dup/182/lib/python3.6/site-packages/duplicity/backend.py", line 557, in get
DUPLICITY: . self.backend._get(remote_filename, local_path)
DUPLICITY: . File "/snap/deja-dup/182/lib/python3.6/site-packages/duplicity/backends/_boto_single.py", line 271, in _get
DUPLICITY: . key_name = self.key_prefix + remote_filename
DUPLICITY: . TypeError: must be str, not bytes
---

*Expected behaviour*

Seamless backup to S3.

*Suggested fix*

In /snap/deja-dup/182/lib/python3.6/site-packages/duplicity/backends/_boto_single.py, wrap all occurences of 'remote_filename' in a call to 'util.fsdecode(...)'.
Potentially, there are other variables concerned as well.

Thanks.