Install chrome native client (nacl)

I am trying to install chrome native client.
I went to this https://developer.chrome.com/native-client/sdk/download page to download and install the sdk. I followed the instructions in this page however when I tried to execute the naclsdk list commnad or any naclsdk command I got an error –

third_party.fancy_urllib.InvalidCertificateException: Host storage.googleapis.com returned an invalid certificate ([SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:661)):
To learn more, see http://code.google.com/appengine/kb/general.html#rpcssl
Usage: sdk_update_main.py [options]

what is the problem here? ,is there a problem with a certificate?

thanks