def load(self, filename, create_if_missing=True):
        filename = Path(filename)
        if not filename.exists() and create_if_missing:
            self.load_pip_requirements()
            with filename.open("w") as f:
                f.write(yaml.dump(self.serialized, default_flow_style=False,
                                  encoding=None))
            self.filename = filename
            return self.save(filename)
        with filename.open() as f:
            for group, requirements in yaml.load(f.read()).items():
                for requirement in requirements:
                    self[group].add(Requirement.coerce(requirement))
        self.filename = filename
def request_message_txt(self):
        """
        This is the body of the request we send across. This is never actually
        used in the code, but exists for debugging purposes -- you can call
        `print attempt.request_message_txt()` on the console and get a readable
        rendering of the request that would be sent across, without actually
        sending anything.
        """
        headers, body = self.create_request()

        header_txt = "\n".join(
            u"{}: {}".format(h, v) for h, v in sorted(headers.items())
        )
        body_txt = json.dumps(body, indent=2, sort_keys=True, ensure_ascii=False).encode('utf-8')

        return header_txt + "\n\n" + body_txt