Add quality checks and fix mypy
- Add editorconfig Make editors behave.
- Add pre-commit config Adds checks and fixers before committing crimes. Run pre-commit install --install-hooks to enable the hooks.
- Use black for formatting
- Add mass mypy fixes
Use PEP484, no implicit Optional - Fix optional bytes of child_process.stdin
Even if subprocess.Popen() does not raise an Exception, there might be no stdin to talk to successfully.