The default Juju config option for `source` is `ppa:canonical-arista/queens-stable` [0].
When deploying on focal without overriding this option this leads to:
2020-09-16 17:12:24 DEBUG neutron-plugin-api-subordinate-relation-changed Err:6 http://ppa.launchpad.net/canonical-arista/queens-stable/ubuntu focal Release
2020-09-16 17:12:24 DEBUG neutron-plugin-api-subordinate-relation-changed 404 Not Found [IP: 91.189.95.83 80]
2020-09-16 17:12:28 DEBUG neutron-plugin-api-subordinate-relation-changed Reading package lists...
2020-09-16 17:12:28 DEBUG neutron-plugin-api-subordinate-relation-changed E: The repository 'http://ppa.launchpad.net/canonical-arista/queens-stable/ubuntu focal Release' does not have a Release file.
2020-09-16 17:12:29 ERROR juju-log neutron-plugin-api-subordinate:33: Hook error:
Traceback (most recent call last):
File "/usr/local/lib/python3.8/dist-packages/charms/reactive/__init__.py", line 74, in main
bus.dispatch(restricted=restricted_mode)
File "/usr/local/lib/python3.8/dist-packages/charms/reactive/bus.py", line 390, in dispatch
_invoke(other_handlers)
File "/usr/local/lib/python3.8/dist-packages/charms/reactive/bus.py", line 359, in _invoke
handler.invoke()
File "/usr/local/lib/python3.8/dist-packages/charms/reactive/bus.py", line 181, in invoke
self._action(*args)
File "/var/lib/juju/agents/unit-neutron-api-plugin-arista-0/charm/reactive/neutron_arista_handlers.py", line 38, in install_arista
charm_class.install()
File "lib/charm/openstack/neutron_arista.py", line 30, in install
apt_update(fatal=True)
File "/usr/local/lib/python3.8/dist-packages/charmhelpers/fetch/ubuntu.py", line 315, in apt_update
_run_apt_command(cmd, fatal)
File "/usr/local/lib/python3.8/dist-packages/charmhelpers/fetch/ubuntu.py", line 776, in _run_apt_command
_run_with_retries(
File "/usr/local/lib/python3.8/dist-packages/charmhelpers/fetch/ubuntu.py", line 756, in _run_with_retries
result = subprocess.check_call(cmd, env=env)
File "/usr/lib/python3.8/subprocess.py", line 364, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['apt-get', 'update']' returned non-zero exit status 100.
0: https://opendev.org/openstack/charm-neutron-api-plugin-arista/src/branch/master/src/config.yaml#L3
