Comment 4 for bug 1788558

Same problem here...

Stacktrace

LFTP version is 4.4.13
Local and Remote metadata are synchronized, no sync needed.
Last full backup left a partial set, restarting.
Last full backup date: Fri Aug 24 01:00:02 2018
RESTART: The first volume failed to upload before termination.
         Restart is impossible...starting backup from beginning.
LFTP version is 4.4.13
Local and Remote metadata are synchronized, no sync needed.
Last full backup date: Thu Aug 23 01:00:01 2018
Traceback (innermost last):
  File "/usr/bin/duplicity", line 1567, in <module>
    with_tempdir(main)
  File "/usr/bin/duplicity", line 1553, in with_tempdir
    fn()
  File "/usr/bin/duplicity", line 1405, in main
    do_backup(action)
  File "/usr/bin/duplicity", line 1523, in do_backup
    full_backup(col_stats)
  File "/usr/bin/duplicity", line 584, in full_backup
    globals.backend)
  File "/usr/bin/duplicity", line 466, in write_multivol
    (tdp, dest_filename, vol_num)))
  File "/usr/lib/python2.7/dist-packages/duplicity/asyncscheduler.py", line 146, in schedule_task
    return self.__run_synchronously(fn, params)
  File "/usr/lib/python2.7/dist-packages/duplicity/asyncscheduler.py", line 172, in __run_synchronously
    ret = fn(*params)
  File "/usr/bin/duplicity", line 465, in <lambda>
    vol_num: put(tdp, dest_filename, vol_num),
  File "/usr/bin/duplicity", line 355, in put
    validate_block(putsize, dest_filename)
  File "/usr/bin/duplicity", line 337, in validate_block
    util.escape(dest_filename), orig_size))
 TypeError: %d format: a number is required, not NoneType

LFTP version is 4.4.13
Local and Remote metadata are synchronized, no sync needed.
Last full backup date: Fri Aug 24 13:50:00 2018
No old backup sets found, nothing deleted.

Command is:

/usr/bin/duplicity full --archive-dir=/root/.duplicity --volsize 1000 --name etc_daily --encrypt-key <somekey> --gpg-options "--homedir=/blah/.gnupg" /etc/ ftp://someuser@$someserver/full