Race condition in ini writing with concurrent use

[JacobHayes]

When using pydna in multiple processes (eg: in tests with pytest-xdist), the ini file may attempt to be written multiple times or read before the default config is written.

Eg, this sequence will cause errors:

• process 1 opens the file in write mode with open(_ini_path, 'w', encoding="utf-8") as f
• process 2 reads the file _parser.read(_ini_path)
• process 1 writes the config _parser.write(f)

resulting in this error:

    from pydna.dseqrecord import Dseqrecord
../venv/lib/python3.10/site-packages/pydna/__init__.py:169: in <module>
    _mainsection = _parser["main"]
../python/lib/python3.10/configparser.py:964: in __getitem__
    raise KeyError(key)
E   KeyError: 'main'

(in process 2, which read the file before the contents were written)

---

As a fix, maybe it could use a tempfile.NamedTemporaryFile and then move it over at the end (which should be atomic on most platforms if we ensure the tempfile is in ini dir / same filesystem) or just skip creating the configuration file completely (eg: stop after _parser["main"] = default_ini)?

I'd be happy to PR either.

[BjornFJohansson]

Thanks for your input! I like the NamedTemporaryFile solution. If you make a PR against the "dev_bjorn" branch, Ill be happy to merge and make a new release.