Custom headers can be added to the default headers.

        Returns a valid requests.Response, raise requests.HTTPError if the status code of the requests.Response
        isn't valid - see response.raise_for_status()

        The caller needs to close the requests.Response

        :param endpoint: string url endpoint
        :param headers: extra headers
        :return: requests.Response

def poll(self, scraper_config, headers=None):
        """
        Custom headers can be added to the default headers.

        Returns a valid requests.Response, raise requests.HTTPError if the status code of the requests.Response
        isn't valid - see response.raise_for_status()

        The caller needs to close the requests.Response

        :param endpoint: string url endpoint
        :param headers: extra headers
        :return: requests.Response
        """
        endpoint = scraper_config.get('prometheus_url')

        # Should we send a service check for when we make a request
        health_service_check = scraper_config['health_service_check']
        service_check_name = '{}{}'.format(scraper_config['namespace'], '.prometheus.health')
        service_check_tags = ['endpoint:{}'.format(endpoint)]
        service_check_tags.extend(scraper_config['custom_tags'])

        try:
            response = self.send_request(endpoint, scraper_config, headers)
        except requests.exceptions.SSLError:
            self.log.error("Invalid SSL settings for requesting {} endpoint".format(endpoint))
            raise
        except IOError:
            if health_service_check:
                self.service_check(service_check_name, AgentCheck.CRITICAL, tags=service_check_tags)
            raise
        try:
            response.raise_for_status()
            if health_service_check:
                self.service_check(service_check_name, AgentCheck.OK, tags=service_check_tags)
            return response
        except requests.HTTPError:
            response.close()
            if health_service_check:
                self.service_check(service_check_name, AgentCheck.CRITICAL, tags=service_check_tags)
            raise