[SSL: CERTIFICATE_VERIFY_FAILED] while connecting through HTTPS under OS X

def _connect_startup_page(self, server_url):
        url = server_url + DRIVE_STARTUP_PAGE
        try:
            proxy_handler = get_proxy_handler(self._manager.get_proxies())
            opener = urllib2.build_opener(proxy_handler)
            log.debug('Proxy configuration for startup page connection: %s, effective proxy list: %r',
                      self._manager.get_proxy_settings().config, get_opener_proxies(opener))
            headers = {
                'X-Application-Name': self._manager.get_appname(),
                'X-Device-Id': self._manager.get_device_id(),
                'X-Client-Version': self._manager.get_version(),
                'User-Agent': self._manager.get_appname() + "/" + self._manager.get_version(),
            }
            req = urllib2.Request(url, headers=headers)
            response = opener.open(req, timeout=STARTUP_PAGE_CONNECTION_TIMEOUT)
            status = response.getcode()
        except urllib2.HTTPError as e:
            status = e.code
        except:
            log.exception('Error while trying to connect to Nuxeo Drive startup page with URL %s', url)
            raise StartupPageConnectionError()
        log.debug('Status code for %s = %d', url, status)
        return status