I faced with broken add-apt-repository on my KDE Neon after upgrading to Ubuntu 22.04

aptsources.distro.NoDistroTemplateException: Error: could not find a distribution template for Neon/jammy

Though I knew that the issue was in /etc/os-release file I wanted to debug add-apt-repository using my favorite debugger.

Naive approach

It’s a python script that comes with Ubuntu to manage repositories from PPA. If it’s a python script it can be debugged with pudb. But first of all we need to install it:

  1. Create a fresh virtual environment:

     virtualenv ~/venvs/pudb
     Created virtual environment CPython3.10.4.final.0-64 in 216ms
     creator CPython3Posix(dest=/home/misharov/venvs/pudb, clear=False, no_vcs_ignore=False, global=False)
     seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/home/misharov/.local/share/virtualenv)
         added seed packages: pip==22.0.2, setuptools==59.6.0, wheel==0.37.1
     activators BashActivator,CShellActivator,FishActivator,NushellActivator,PowerShellActivator,PythonActivator
    
  2. Activate it:

     source /home/misharov/venvs/pudb/bin/activate
    
  3. Install pudb:

     pip install pudb
    
  4. Run add-apt-repository in the debug mode. The naive approach would be running the script like this:

     python -m pudb /usr/bin/add-apt-repository
    

It will be executed until you will get the following error:

ModuleNotFoundError: No module named 'apt_pkg'

Ouch, the naive approach was wrong. Our virtual environment is not aware about system installed packages. In Ubuntu 22.04 system python packages are installed in the following paths:

python3 -c 'import site; print(site.getsitepackages())'
['/usr/local/lib/python3.10/dist-packages', '/usr/lib/python3/dist-packages', '/usr/lib/python3.10/dist-packages']

apt_pkg can be found in /usr/lib/python3/dist-packages

The right way

Someone would propose to install pudb along with system python packages but it might even break the system python. Therefore never run sudo pip install! There is a better way. virtualenv can create a virtual environment that uses system packages:

virtualenv --system-site-packages ~/venvs/pudb
created virtual environment CPython3.10.4.final.0-64 in 114ms
  creator CPython3Posix(dest=/home/misharov/venvs/pudb, clear=False, no_vcs_ignore=False, global=True)
  seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/home/misharov/.local/share/virtualenv)
    added seed packages: pip==22.0.2, setuptools==59.6.0, wheel==0.37.1
  activators BashActivator,CShellActivator,FishActivator,NushellActivator,PowerShellActivator,PythonActivator

New packages will be installed into the virtual environment and system packages will be accounted as well. After activation and installation pudb we can run add-apt-repository in the debug mode.

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