# error: subprocess-exited-with-error

× python setup.py egg_info did not run successfully.
│ exit code: 1
╰─> [12 lines of output]
    ModuleNotFoundError: No module named 'Cython'

note: This error originates from a subprocess, and is likely not a problem with pip.
ERROR: Failed building wheel for somepkg

- **ID:** `python/pip-subprocess-exited-with-error-metadata`
- **Domain:** python
- **Category:** install_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

A source distribution's build step requires build-time dependencies (Cython, numpy headers, etc.) that are not declared in pyproject.toml [build-system].requires and not present in the current environment.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.8 | active | — | — |
| 3.9 | active | — | — |
| 3.10 | active | — | — |
| 3.11 | active | — | — |
| 3.12 | active | — | — |

## Workarounds

1. **** (90% success)
   ```
   pip install Cython numpy
pip install somepkg
   ```
2. **** (85% success)
   ```
   pip install --only-binary=:all: somepkg
# or specify a wheel index
pip install --index-url https://download.pytorch.org/whl/cpu somepkg
   ```

## Dead Ends

- **** — The missing module is Cython, not pip/setuptools; upgrading build tools does not install Cython. (80% fail)
- **** — Disabling build isolation uses the current env, which also lacks Cython, so the same ModuleNotFoundError occurs. (70% fail)