mitogen: apt: AttributeError: module '__main__' has no attribute '_module_fqn'

• Which version of Ansible are you running?

ansible [core 2.11.2] 
  config file = ~/.ansible.cfg
  configured module search path = ['~/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/venv/lib/python3.9/site-packages/ansible
  ansible collection location = ~/.ansible/collections:/usr/share/ansible/collections
  executable location = /usr/local/venv/bin/ansible
  python version = 3.9.6 (default, Jul 16 2021, 00:00:00) [GCC 11.1.1 20210531 (Red Hat 11.1.1-3)]
  jinja version = 3.0.1
  libyaml = True

• Is your version of Ansible patched in any way? no
• Are you running with any custom modules, or module_utils loaded? no
• Have you tried the latest master version from Git? yes
• Mention your host and target OS and versions
  • host: Fedora 34
  • target: Debian 10 docker image
• Mention your host and target Python versions
  • host: Python 3.9
  • target: Python 3.7

Example Playbook:

---
- name: Converge
  hosts: all

  tasks:
    - name: install vim
      ansible.builtin.apt:
        name: vim
        state: present

Error:

The full traceback is:
Traceback (most recent call last):
  File "master:/usr/local/share/mitogen/ansible_mitogen/runner.py", line 975, in _run
    self._run_code(code, mod)
  File "master:/usr/local/share/mitogen/ansible_mitogen/runner.py", line 939, in _run_code
    exec(code, vars(mod))
  File "master:/usr/local/venv/lib/python3.9/site-packages/ansible/modules/apt.py", line 1310, in <module>
  File "master:/usr/local/venv/lib/python3.9/site-packages/ansible/modules/apt.py", line 1114, in main
  File "master:/usr/local/venv/lib/python3.9/site-packages/ansible/module_utils/common/respawn.py", line 39, in respawn_module
    payload = _create_payload()
  File "master:/usr/local/venv/lib/python3.9/site-packages/ansible/module_utils/common/respawn.py", line 76, in _create_payload
    module_fqn = sys.modules['__main__']._module_fqn
AttributeError: module '__main__' has no attribute '_module_fqn'
fatal: [linux-debian-10]: FAILED! => {
    "ansible_facts": {},
    "changed": false,
    "module_stderr": "Traceback (most recent call last):\n  File \"master:/usr/local/share/mitogen/ansible_mitogen/runner.py\", line 975, in _run\n    self._run_code(code, mod)\n  File \"master:/usr/local/share/mitogen/ansible_mitogen/runner.py\", line 939, in _run_code\n    exec(code, vars(mod))\n  File \"master:/usr/local/venv/lib/python3.9/site-packages/ansible/modules/apt.py\", line 1310, in <module>\n  File \"master:/usr/local/venv/lib/python3.9/site-packages/ansible/modules/apt.py\", line 1114, in main\n  File \"master:/usr/local/venv/lib/python3.9/site-packages/ansible/module_utils/common/respawn.py\", line 39, in respawn_module\n    payload = _create_payload()\n  File \"master:/usr/local/venv/lib/python3.9/site-packages/ansible/module_utils/common/respawn.py\", line 76, in _create_payload\n    module_fqn = sys.modules['__main__']._module_fqn\nAttributeError: module '__main__' has no attribute '_module_fqn'\n",
    "module_stdout": "",
    "msg": "MODULE FAILURE\nSee stdout/stderr for the exact error",
    "rc": 1
}

Verbose output: verbose.log.txt

Workarounds like:

1. Adding vars: { mitogen_task_isolation: fork } to the task
2. Adding ansible.builtin.apt to ALWAYS_FORK_MODULES in ansible_mitogen/planner.py

doesn’t work.