Construct the user-agent header with the package info,
        Python version and OS version.

        Returns:
            The user agent string.
            e.g. 'Python/3.6.7 slack/2.0.0 Darwin/17.7.0'

def _get_user_agent():
        """Construct the user-agent header with the package info,
        Python version and OS version.

        Returns:
            The user agent string.
            e.g. 'Python/3.6.7 slack/2.0.0 Darwin/17.7.0'
        """
        # __name__ returns all classes, we only want the client
        client = "{0}/{1}".format(__name__.split(".")[0], ver.__version__)
        python_version = "Python/{v.major}.{v.minor}.{v.micro}".format(
            v=sys.version_info
        )
        system_info = "{0}/{1}".format(platform.system(), platform.release())
        user_agent_string = " ".join([python_version, client, system_info])
        return user_agent_string