Fix CommandNotFound.py crash

Issue

If an unknown command is typed, a crash message is displayed.

u505@naos:~$ unknowncommand
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: 3.9.1 final 0
Distributor ID: Kali
Description:    Kali GNU/Linux Rolling
Release:        2020.4
Codename:       kali-rolling
Exception information:


unable to open database file
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 90, in main
    cnf = CommandNotFound.CommandNotFound(options.data_dir)
  File "/usr/share/command-not-found/CommandNotFound/CommandNotFound.py", line 79, in __init__
    self.db = SqliteDatabase(dbpath)
  File "/usr/share/command-not-found/CommandNotFound/db/db.py", line 12, in __init__
    self.con = sqlite3.connect(filename)
sqlite3.OperationalError: unable to open database file

Problem

The problem is that the user doesn't have the correct rights to open the commands.db SQLite database.

u505@naos:~$ grep dbpath /usr/share/command-not-found/CommandNotFound/CommandNotFound.py
dbpath = "/var/lib/command-not-found/commands.db"
        if os.path.exists(dbpath):
            self.db = SqliteDatabase(dbpath)
u505@naos:~$ ls -l /var/lib/command-not-found/commands.db
-rw-r----- 1 root root 2650112 Jan 24 00:14 /var/lib/command-not-found/commands.db

Fix

Correct the databse right, to allow everybody read access.

u505@naos:~$ sudo chmod 644 /var/lib/command-not-found/commands.db
u505@naos:~$ ls -l /var/lib/command-not-found/commands.db
-rw-r--r-- 1 root root 2650112 Jan 24 00:14 /var/lib/command-not-found/commands.db

Once the file is available for users, the crash disappears.

u505@naos:~$ unknowncommand
unknowncommand: command not found

References

• Debian command-not-found error - local variable 'cnf' referenced before assignment