Get UPS HTTP session.

def get_session(username, password, locale=DEFAULT_LOCALE,
                cookie_path=COOKIE_PATH):
    """Get UPS HTTP session."""
    class UPSAuth(AuthBase):  # pylint: disable=too-few-public-methods
        """UPS authorization storage."""

        def __init__(self, username, password, locale, cookie_path):
            """Init."""
            self.username = username
            self.password = password
            self.locale = locale
            self.cookie_path = cookie_path

        def __call__(self, r):
            """Call is no-op."""
            return r

    session = requests.session()
    session.auth = UPSAuth(username, password, locale, cookie_path)
    if os.path.exists(cookie_path):
        session.cookies = _load_cookies(cookie_path)
    else:
        _login(session)
    return session