It seems that pwb.py cannot import httplib2 from externals directory.
And after installed the httplib2, the error appears.
I then try to use the pip one, same happened.
And the error is a little different than the one said, it's
{FatalServerError: [Errno 1] _ssl.c:504: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed}, instead of SSLHandshakeError.