python2_dnf is not available for Fedora 30 (rawhide)

[robertdebock]

SUMMARY

Fedora 30 (now rawhide, the unreleased development branch) will not offer python2-dnf anymore.

This causes a problem when installing python2 on Fedora 30.

ISSUE TYPE

• Bug Report

COMPONENT NAME

dnf

ANSIBLE VERSION

ansible 2.7.1
  config file = None
  configured module search path = [u'/home/robertdb/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.15 (default, Oct 15 2018, 15:26:09) [GCC 8.2.1 20180801 (Red Hat 8.2.1-2)]

CONFIGURATION

[no output]

OS / ENVIRONMENT

Control node does not matter, I'm using Fedora 29.
Managed node: Fedora 30/rawhide

STEPS TO REPRODUCE

Start a fedora rawhide container:

docker run --rm fedora:rawhide sleep 300

Install python2 on it:

ansible \
  -m dnf \
  -a "name=python2" \
  -i f9f2e079d337, \
  -c docker \
  -e "ansible_python_interpreter=/usr/bin/python3" \
  all

Install another package using the default ansible_python_interpreter:

ansible \
  -m dnf \
  -a "name=sos" \
  -i f9f2e079d337, \
  -c docker \
  all

Another way to test this: (could be used in the integration tests)

# INSTALLPYTHON2
#  The module `dnf` tries to install python2-dnf when it's running on systems
#  that have python2 installed. Fedora 30 and newer have python3 and limited
#  support for python2, for example python2-dnf is missing.

- name: use python3
  set_fact:
    ansible_python_interpreter: /usr/bin/python3

- name: install python2
  dnf:
    name: python2
    state: present

- name: use python2
  set_fact:
    ansible_python_interpreter: /usr/bin/python

- name: install a sample package
  dnf:
    name: python2
    state: present

EXPECTED RESULTS

Just to have python2 installed, I'm not interested in python2-dnf.

I realize this an edge case, and fixing it may cause more issues, like #22305.

ACTUAL RESULTS

f9f2e079d337 | FAILED! => {
    "changed": false, 
    "cmd": "dnf install -y python2-dnf", 
    "msg": "Error: Unable to find a match", 
    "rc": 1, 
    "stderr": "Error: Unable to find a match\n", 
    "stderr_lines": [
        "Error: Unable to find a match"
    ], 
    "stdout": "Last metadata expiration check: 0:01:03 ago on Fri Nov 30 10:19:16 2018.\nNo match for argument: python2-dnf\n", 
    "stdout_lines": [
        "Last metadata expiration check: 0:01:03 ago on Fri Nov 30 10:19:16 2018.", 
        "No match for argument: python2-dnf"
    ]
}

[ansibot]

Hi @robertdebock, thank you for submitting this issue!

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[ansibot]

Files identified in the description:

• lib/ansible/modules/packaging/os/dnf.py

If these files are inaccurate, please update the component name section of the description or use the !component bot command.

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[maxamillion]

Ultimately I think the issue here is that Fedora is moving away from python2 and there's nothing Ansible can realistically do.

[ansibot]

cc @DJMuggs @berenddeschouwer @ignatenkobrain
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[imp1sh]

Ultimately I think the issue here is that Fedora is moving away from python2 and there's nothing Ansible can realistically do.

Python2 is loosing support next year so everybody is being forced to drop python2 support for everything. Why not just install python3-dnf instead of python2-dnf?
In my case I'm not even trying to install anything python2 related but only try to use the dnf module which seems to rely on python2_dnf which I think is wrong.

[jborean93]

@imp1sh the problem is that you are trying to run the dnf module with /use/bin/python which is Python 2. The module just checks on the Python version that is currently running and if it’s Python 2 it will attempt to install python2-dnf which is no longer available in recent Fedora versions.

The dnf module can’t change interpreters as it is not in charge of that proves so you must do it yourself by either;

• Set the interpreter explicitly to the Python interpreter you want with the var ansible_python_interpreter: /use/bin/python3, or
• Opt out of the legacy behaviour and get Ansible to dynamically choose the best Python interpreter for the district with ansible_python_interpreter: auto

The latter option will be the new default in Ansible 2.12 but because it is a change in behaviour we had to have a deprecation period since it was introduced in Ansible 2.8. You can read more about python interpreter discovery here.