Document the current practice for SystemError

@malemburg pointed that the documentation of SystemError only refers to CPython internal errors as the source.

https://docs.python.org/3/library/exceptions.html#SystemError

On practice, SystemError is also raised on improper use of the C API (like NULL pointer, or negative size, or wrong type in the concrete API) if it is possible to detect such error and it is not too costly (macros usually lack any argument checks). An alternative to SystemError is a crash or memory corruption. Currently the main source of SystemError is errors in third-party extensions, not in the Python core or standard extensions.

The documentation looks outdated, perhaps it predates the public C API.

Commencez par la section SystemError à l’adresse docs.python.org/3/library/exceptions.html#SystemError et examinez la description de l’issue concernant l’utilisation incorrecte de la C API. Mettez à jour la documentation afin qu’elle reflète la pratique actuelle indiquée, y compris les utilisations incorrectes détectables dans les extensions, et assurez-vous que le texte qui en résulte n’implique plus que les erreurs internes de CPython en sont l’unique source.