test_async_query_callback fails: session fixture can't find .env #393

tests/frontend/test_callback.py::test_async_query_callback errors at setup (not a test failure, a fixture error). Docker is running, so this is not the usual "Docker not up" case — the session fixture in tests/conftest.py cannot find a .env file, and the subsequent docker-compose ... port r3 8080 lookup exits non-zero.

Repro

pytest tests/frontend/test_callback.py::test_async_query_callback

Error

ERROR at setup of test_async_query_callback

request = <SubRequest 'session' for <Function test_async_query_callback>>
>   nn_service_name = compose.get_service_host(service_name="r3", port=8080)
tests/conftest.py:23:
...
>   raise CalledProcessError(retcode, process.args, ...)
E   subprocess.CalledProcessError: Command '['docker-compose', '-f', 'docker-compose-test.yml',
E     '--env-file', '.env', 'port', 'r3', '8080']' returned non-zero exit status 1.

---------------------------- Captured stderr setup -----------------------------
starting docker container
couldn't find env file: .../.env
couldn't find env file: .../.env
couldn't find env file: .../.env

Notes

• The session fixture (tests/conftest.py:~19) constructs DockerCompose(filepath=".", compose_file_name="docker-compose-test.yml", env_file=".env", build=True, pull=True). There is no .env in the repo (only sample.env), so the --env-file .env argument fails and the port r3 8080 call returns exit 1.
• Likely fixes to consider later: provide/generate a .env (or point env_file at sample.env), or skip the test cleanly when no .env/compose stack is available (this test was previously marked skip).

Not fixing now — filing for later.