Unicode error when source directory contains non-ascii character

When trying to back up a directory that contains a non-ascii character , duplicity fails with this message:

/snap/duplicity/33/bin/duplicity:64: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
  if u'--pydevd' in sys.argv or os.getenv(u'PYDEVD', None):
Traceback (innermost last):
  File "/snap/duplicity/33/bin/duplicity", line 101, in <module>
    with_tempdir(main)
  File "/snap/duplicity/33/bin/duplicity", line 87, in with_tempdir
    fn()
  File "/snap/duplicity/current/lib/python2.7/site-packages/duplicity/dup_main.py", line 1526, in main
    action = commandline.ProcessCommandLine(sys.argv[1:])
  File "/snap/duplicity/current/lib/python2.7/site-packages/duplicity/commandline.py", line 1137, in ProcessCommandLine
    args = parse_cmdline_options(cmdline_list)
  File "/snap/duplicity/current/lib/python2.7/site-packages/duplicity/commandline.py", line 745, in parse_cmdline_options
    if u'://' not in args[loc]:
 UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 14: ordinal not in range(128)

I use 0.8.08 (installed via snap)
Python 2.7.15+ (that comes bundled with that snap)
Ubuntu 19.10
Target filesystem doesn't seem to matter, happens with local directory as target as well as with S3
Logs:
duplicity -v9 testö file://target/
/snap/duplicity/33/bin/duplicity:64: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
  if u'--pydevd' in sys.argv or os.getenv(u'PYDEVD', None):
Temporäres Verzeichnis /tmp/duplicity-0KPd5Q-tempdir wird benutzt
Traceback (innermost last):
  File "/snap/duplicity/33/bin/duplicity", line 101, in <module>
    with_tempdir(main)
  File "/snap/duplicity/33/bin/duplicity", line 87, in with_tempdir
    fn()
  File "/snap/duplicity/current/lib/python2.7/site-packages/duplicity/dup_main.py", line 1526, in main
    action = commandline.ProcessCommandLine(sys.argv[1:])
  File "/snap/duplicity/current/lib/python2.7/site-packages/duplicity/commandline.py", line 1137, in ProcessCommandLine
    args = parse_cmdline_options(cmdline_list)
  File "/snap/duplicity/current/lib/python2.7/site-packages/duplicity/commandline.py", line 688, in parse_cmdline_options
    possible = [c for c in commands if c.startswith(cmd)]
 UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 4: ordinal not in range(128)