I saw this again in a container, and it is easy to reproduce now.

Just install the package 'aspell-is' that includes filename 'usr/lib/aspell/\xedslenska.alias' and running /usr/lib/cnf-update-db
will fail:

(extra output is my custom print() in creator.py line 241)
l: b'usr/lib/aspell/xh.dat\t\t\t\t\t universe/text/aspell-xh\n'
l: b'usr/lib/aspell/xh.multi\t\t\t\t\t universe/text/aspell-xh\n'
l: b'usr/lib/aspell/xh.rws\t\t\t\t\t universe/text/aspell-xh\n'
l: b'usr/lib/aspell/xhosa.alias\t\t\t\t universe/text/aspell-xh\n'
l: b'usr/lib/aspell/zu.dat\t\t\t\t\t universe/text/aspell-zu\n'
l: b'usr/lib/aspell/zu.multi\t\t\t\t\t universe/text/aspell-zu\n'
l: b'usr/lib/aspell/zu.rws\t\t\t\t\t universe/text/aspell-zu\n'
l: b'usr/lib/aspell/zulu.alias\t\t\t\t universe/text/aspell-zu\n'
l: b'usr/lib/aspell/\xedslenska.alias\t\t\t\t universe/text/aspell-is\n' Traceback (most recent call last):
File "/usr/lib/cnf-update-db", line 32, in <module>
col.create(db)
~~~~~~~~~~^^^^
File "/usr/share/command-not-found/CommandNotFound/db/creator.py",
line 96, in create
self._fill_commands(con)
~~~~~~~~~~~~~~~~~~~^^^^^
File "/usr/share/command-not-found/CommandNotFound/db/creator.py",
line 141, in _fill_commands
self._parse_single_contents_file(con, f, sub.stdout)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
File "/usr/share/command-not-found/CommandNotFound/db/creator.py",
line 242, in _parse_single_contents_file
l = l.decode("utf-8")
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xed in position
15: invalid continuation byte

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)