Invoking "python" brings inappropriate response from command-not-found when python3 installed

$ apt policy python3-commandnotfound
python3-commandnotfound:
  Installed: 19.10.0
  Candidate: 19.10.0
  Version table:
 *** 19.10.0 500
        500 http://gb.archive.ubuntu.com/ubuntu focal/main amd64 Packages
        500 http://gb.archive.ubuntu.com/ubuntu focal/main i386 Packages
        100 /var/lib/dpkg/status

Status changed to 'Confirmed' because the bug affects multiple users.

Confirming this bug: "python3" installed, but "python" command not found after I upgraded my Ubuntu-MATE 18.04 to 20.04. I realise that Python 2 is being deprecated in 20.04, but there should be a default "python" command, so I added a Debian alternative:

update-alternatives --install /usr/bin/python python-interpreter /usr/bin/python3 90

The solution for this will be for us to provide a python-is-python3 package, not installed by default, which command-not-found will then offer.

This will NOT be managed as an alternative.

The asciicinema stuff has disappeared but I presume this is the output:

 $ python

Command 'python' not found, but can be installed with:

sudo apt install python3 # version 3.7.5-1ubuntu1, or
sudo apt install python # version 2.7.17-1
sudo apt install python-minimal # version 2.7.17-1

You also have python3 installed, you can run 'python3' instead.

Indeed. It offers python3 version 3.7.5-1ubuntu1 as a solution which is not appropriate as python3 version 3.8.0-3 is already installed and does not provide a `python` command.

The python-is-python3 solution sounds like a sensible way forward. There be dragons, I suspect.

Using 20.04 current build still see:

$ python

Command 'python' not found, but can be installed with:

If I run sudo apt install python

Package python is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
  python2-minimal:i386 python2:i386 python2-minimal python2 2to3

E: Package 'python' has no installation candidate

This has an effect on an upgrade to 20.04 of uninstalling any package that depends on "python" for example slack-desktop.

Expected behaviour is:

$ python

Command 'python' not found, did you mean:

  command 'python3' from deb python3 (3.8.2-0ubuntu1)

Try: sudo apt install <deb name>

$ python
Command 'python' not found, did you mean:

  command 'python3' from deb python3

Is the new behaviour

This bug was fixed in the package command-not-found - 20.04.0

---------------
command-not-found (20.04.0) focal; urgency=medium

  * Special case python -> python3, using existing translated strings. LP:
    #1306682, LP: #1863532

 -- Dimitri John Ledkov <email address hidden> Thu, 12 Mar 2020 13:10:32 +0000

Dimitri, this is contrary to the plan of record. Please revert.

The expected behavior is that typing 'python' recommends installing the python3-is-python package, /which needs to be added to the archive/.

Correction: 'python-is-python3'

Current behavior on focal:

$ python

Command 'python' not found, did you mean:

  command 'python3' from deb python3
  command 'python ' from deb python-is-python3

$

There's an extra space in the name 'python ', can we get this fixed?

the current aligned output is more readable. So either leave it this way, or keep it aligned while removing the space within the quotes.

@vorlon

I've played with output about a dozen times. All other output from command not found is always aligned. It looks very odd when the output looks like a Christmas tree, without breaking translations.

maybe we can specify format padding around '%s'