重试逻辑fix

Author: libertyzhu

qcloud_cos/cos_client.py

@@ -375,14 +375,14 @@ def send_request(self, method, url, bucket, timeout=30, cos_request=True, ci_req
                     res = self._session.head(url, timeout=timeout, proxies=self._conf._proxies, **kwargs)
                 if res.status_code < 400:  # 2xx和3xx都认为是成功的
                     if res.status_code == 301 or res.status_code == 302 or res.status_code == 307:
-                        if j < self._retry and res.headers['x-cos-request-id'] == '' \
+                        if j < self._retry and not 'x-cos-request-id' in res.headers \
                             and not domain_switched and self._conf._auto_switch_domain_on_retry and self._conf._ip is None:
                             url = switch_hostname_for_url(url)
                             domain_switched = True
                             continue
                     return res
                 elif res.status_code < 500:  # 4xx 不重试
-                    if j < self._retry and res.headers['x-cos-request-id'] == '' \
+                    if j < self._retry and not 'x-cos-request-id' in res.headers \
                         and not domain_switched and self._conf._auto_switch_domain_on_retry and self._conf._ip is None:
                         url = switch_hostname_for_url(url)
                         domain_switched = True