Error with https://fewa.itris.ch/users/main/join.html

exception = HTTPSConnectionPool(host='fewa.itris.ch', port=443): Max retries exceeded with url: /users/main/join.html (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:992)')))