SSL3_GET_SERVER_CERTIFICATE 错误解决办法

requests模块之前一直正常的，某一天开始对https的请求都抛错误了：
requests.exceptions.SSLError: [Errno 1] _ssl.c:504: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
完整的：

/usr/local/lib/python2.7/dist-packages/requests/packages/urllib3/util/ssl_.py:79: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.
  InsecurePlatformWarning
Traceback (most recent call last):
  File "", line 1, in 
  File "/usr/local/lib/python2.7/dist-packages/requests/api.py", line 68, in get
    return request('get', url, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests/api.py", line 50, in request
    response = session.request(method=method, url=url, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests/sessions.py", line 464, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests/sessions.py", line 576, in send
    r = adapter.send(request, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests/adapters.py", line 431, in send
    raise SSLError(e, request=request)
requests.exceptions.SSLError: [Errno 1] _ssl.c:504: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

试过：

sudo apt-get install ca-certificates
sudo update-ca-certificates

没效果，
最后试了下面的起效的：

sudo pip uninstall -y certifi
sudo pip install certifi==2015.04.28

当然，还是有警告：

/usr/local/lib/python2.7/dist-packages/requests/packages/urllib3/util/ssl_.py:79: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.
  InsecurePlatformWarning

不够，至少可以先用着了。原因估计就是高版本（2016.2.8）的certifi对证书验证更为严格了。