Using --become for ansible_connection=local - ansible

Question

With a personal user account (userx) I run the ansible playbook on all my specified hosts. In ansible.cfg the remote user (which can become root) to be used is:
remote_user = ansible
For the remote hosts this all works fine. It connects as the user Ansible, and executes all tasks as wished for, also changing information (like /etc/ssh/sshd_config) which requires root rights.
But now I also want to execute the playbook on the Ansible host itself. I put the following in my inventory file:
localhost ansible_connection=local
which now indeed executes on localhost. But as userx, and this results in "Access denied" for some task it needs to do.
This is of course somewhat expected, since remote_user tells something about remote, not the local user. But still, I expected that the playbook would --become locally too, to execute the tasks as root (e.g. sudo su -). It seems no to do that.
Running the playbook with --become -vvv tells me
<localhost> ESTABLISH LOCAL CONNECTION FOR USER: userx
and it seems not to try to execute the tasks with sudo. And without using sudo, the task fails.
How can I tell ansible to to use sudo / become on the local connection too?

Answer 1

Nothing special is required. Proof:
The playbook:
---
- hosts: localhost
gather_facts: no
connection: local
tasks:
- command: whoami
register: whoami
- debug:
var: whoami.stdout
The execution line:
ansible-playbook playbook.yml --become
The result:
PLAY [localhost] ***************************************************************************************************
TASK [command] *****************************************************************************************************
changed: [localhost]
TASK [debug] *******************************************************************************************************
ok: [localhost] => {
"changed": false,
"whoami.stdout": "root"
}
PLAY RECAP *********************************************************************************************************
localhost : ok=2 changed=1 unreachable=0 failed=0
The ESTABLISH LOCAL CONNECTION FOR USER: message will always show the current user, as it the account used "to connect".
Later the command(s) called from the module get(s) executed with elevated permissions.
Of course, you can add become: yes on either play level or for individual tasks.