Problem with sudo apt update in Ubuntu 18.04: Post-Invoke-Success if /usr/bin/test -w /var/lib/command-not-found/

The terminal gave me these errors when updating the software with sudo apt update.

Hit:1 http://it.archive.ubuntu.com/ubuntu bionic InRelease
Hit:2 http://it.archive.ubuntu.com/ubuntu bionic-updates InRelease                                                                                       
Hit:3 http://it.archive.ubuntu.com/ubuntu bionic-backports InRelease                                                                                     
Hit:4 http://security.ubuntu.com/ubuntu bionic-security InRelease                                     
Hit:5 http://archive.canonical.com/ubuntu bionic InRelease                
Traceback (most recent call last):                    
  File "/usr/lib/cnf-update-db", line 8, in <module>
    from CommandNotFound.db.creator import DbCreator
ModuleNotFoundError: No module named 'CommandNotFound'
Reading packages list... Done
E: Problem executing scripts APT::Update::Post-Invoke-Success   
 'if /usr/bin/test -w /var/lib/command-not-found/ -a -e /usr/lib/cnf-update-db;     
 then /usr/lib/cnf-update-db > /dev/null; fi'  
E: Sub-process returned an error code  

These are the results of sudo apt install --reinstall command-not-found

Reading package lists... Done 
Building dependency tree        
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded.
Need to get 0 B/5.188 B of archives
After this operation, 0 B of additional disk space will be used.
(Reading the database ... 225797 files and directories currently installed.)
Preparations for extracting ... / command-not-found_18.04.4_all.deb ...
Extracting command-not-found (18.04.4) on (18.04.4) ...
Configuring command-not-found (18.04.4) ...
libdvd-pkg: Package libdvdcss2-1.4.2-1 was removed, stop processing...

When I tried the command sudo apt update again after reinstalling command-not-found, the results were the same as described in the first text block.

Solution 1:

In all currently supported versions of Ubuntu open the terminal and type:

apt download python3-minimal
sudo apt install --reinstall ./python3-minimal_*.deb
sudo apt install -f

If that doesn't work a simple reboot will sometimes solve this problem.

Solution 2:

This solved my same/similar issue:

cd /usr/lib/python3/dist-packages
ls -la /usr/lib/python3/dist-packages
sudo cp apt_pkg.cpython-36m-x86_64-linux-gnu.so apt_pkg.so

Source: Linux Question