Python template makes `readOnly`+`required` fields required for requests. Does not respect openapi 3.0.3

Openapi 3.0.3 says a readOnly and required field is only required in responses, not in requests. The Python template does not make this distinction and generates code such as

    @field.setter
    def field(self, field):
        """Sets the field of this Model.


        :param field: The field of this Model.  # noqa: E501
        :type: str
        """
        if field is None:
            raise ValueError("Invalid value for `field`, must not be `None`")  # noqa: E501

        self._field = field

It's not possible to create an instance of Model without field for a request.

No file or test is named in the issue. Start by locating the Python template logic that turns required fields into constructor or setter validation, then compare its handling of readOnly fields with OpenAPI 3.0.3. Done means a readOnly and required field is optional when creating requests while remaining required in responses, with a regression test covering the generated model.