[hiteshkava]

Description

Upgrades the xqwatcher Ansible role to provision Python 3.12, following
the same pattern as the xqueue role's Python 3.12 upgrade
(#386).

Changes

File	Change	Why
playbooks/roles/xqwatcher/defaults/main.yml	xqwatcher_python_version: python3.8 → python3.12; added xqwatcher_use_python312: true flag	Controls the interpreter for the main watcher venv (deploy_watcher.yml)
playbooks/roles/xqwatcher/tasks/main.yml	Added deadsnakes PPA + python3.12-dev apt-install task	This role had no Python-interpreter install task at all before this change — it relied entirely on the base AMI's default system Python (python3.8 on Focal). Bumping the variable alone, without this, would have silently broken provisioning on a fresh AMI, since Jammy doesn't ship python3.12 by default

Testing

• Verified via Launchpad's API that deadsnakes publishes python3.12-dev for Jammy, confirming the new apt-install task will resolve
• Could not run the actual Ansible playbook against a real instance from this environment — recommend a test AMI build before merging (same test-plan gap noted on the related xqueue PR's own description pattern)

Related PRs

• Application code: feat: add Python 3.12 support and drop Python 3.8 xqueue-watcher#1
• GoCD AMI pipeline: https://github.com/edx/edx-internal/pull/14969
• Reference (same pattern, different service): feat: upgrade xqueue to Python 3.12 #386

Out of scope

• Per-course grader sandboxes (MITx-7.QBWx, MITx-6.00x) used a separate PYTHON_EXECUTABLE/PYTHON_REQUIREMENTS pin in edx-internal's XQWATCHER_COURSES, not controlled by this role change. Management team has confirmed that both courses are no longer active and that MITx has been offboarded from the partnership, so there will be no new runs. The companion edx-internal PR removes them from XQWATCHER_COURSES.