I wonder if an empty #Python pyproject.toml should do this rather than throwing an error:
```
pip install .
Processing c:\git\packaging-test-1
Installing build dependencies ... done
Getting requirements to build wheel ... done
Preparing metadata (pyproject.toml) ... done
Building wheels for collected packages: UNKNOWN
Building wheel for UNKNOWN (pyproject.toml) ... done
Created wheel for UNKNOWN: filename=unknown-0.0.0-py3-none-any.whl size=928 sha256=1d0e48ad7c8a1aa1043cc946258841edf77c58d2ea72d0faed35c39a55c39516
Stored in directory: c:\users\adam\appdata\local\pip\cache\wheels\1d\30\a5\1a2d6d43498e69d78a57a028ad948074f5b0d30a57d085cc40
Successfully built UNKNOWN
Installing collected packages: UNKNOWN
Successfully installed UNKNOWN-0.0.0
```
