1👍
Turned out the ca_certs was missing. The problem is fixed by replacing
client = httplib2.Http()
in line 42 and 52 of allauth/socialaccount/requests.py with
client = httplib2.Http(ca_certs=PATH_TO_YOUR_CERT_FILE)
The CERT_FILE would be the cacert.pem file in the certifi (can be installed via pip or macports, etc.) module.
Seems to be an ugly hack, hope for better solutions.
Source:stackexchange.com