## TL;DR
Run `python -m pip install execnet`, or reinstall pytest-xdist cleanly: `python -m pip install --force-reinstall pytest-xdist`. execnet is xdist's worker-communication dependency; a partial or `--no-deps` install leaves it missing.

```text
ModuleNotFoundError: No module named 'execnet'
```

## Fix it

1. **Install the missing dependency.** Run `python -m pip install execnet`.
   - Expected: `Successfully installed execnet-...`.

2. **Or reinstall the plugin with deps.** Run `python -m pip install --force-reinstall pytest-xdist`.
   - Expected: both pytest-xdist and execnet installed.

3. **Verify.** Run `pytest -n 2 --collect-only -q`.
   - Expected: collection succeeds, workers spawn.

## When this applies
- xdist is installed but workers fail immediately importing execnet.
- You installed with `--no-deps` or copied site-packages by hand.

## When it does not apply
- If xdist itself is missing, install pytest-xdist first.

## Tool compatibility
pytest-xdist 3.x requires execnet. Python 3.8+.

## Why it happens
pip normally installs dependencies automatically, but `--no-deps`, `--target` hacks, or vendored environments can skip execnet while keeping xdist.

## Edge cases
- Some minimal Docker images strip deps; add execnet explicitly to requirements.