Faced the same issue. Details are as follows:
$ ll
Could not find the database of available applications, run update-
command-not-found as root to fix this
Sorry, command-not-found has crashed! Please file a bug report at:
http://www.debian.org/Bugs/Reporting
Please include the following information with the report:
command-not-found version: 0.3
Python version: 3.7.2 final 0
Distributor ID: PureOS
Description: PureOS GNU/Linux 8
Release: 8
Codename: green
Exception information:
local variable 'cnf' referenced before assignment
Traceback (most recent call last):
File "/usr/share/command-not-found/CommandNotFound/util.py", line 23,
in crash_guard
callback()
File "/usr/lib/command-not-found", line 93, in main
if not cnf.advise(args[0], options.ignore_installed) and not
options.no_failure_msg:
UnboundLocalError: local variable 'cnf' referenced before assignment
As mentioned in the description I tried running update-command-not-
found as root and it did not make any difference.
