Authenticate with Opsview
        :param verbose: Verbose output mode
        :type verbose: bool
        :return: The authentification token
        :rtype: str or unicode

def login(self, verbose=False):
        '''
        Authenticate with Opsview
        :param verbose: Verbose output mode
        :type verbose: bool
        :return: The authentification token
        :rtype: str or unicode
        '''
        url = '{}/{}'.format(self.rest_url, 'login')
        logger.debug('POST: {}'.format(url))
        r = requests.post(url, json={
                'username': self.username,
                'password': self.password
            },
            verify=self.verify_ssl
        )
        j = r.json()
        logger.debug('Request response:')
        logger.debug(pformat(vars(r)))
        logger.debug('JSON:')
        logger.debug(pformat(j))
        if 'token' not in j:
            raise OpsviewLoginException("Failed to retrieve token. "
                                        "Please check your credentials")
        self.headers['X-Opsview-Token'] = j['token']
        self._token_age = datetime.datetime.now()
        return j['token']