SSLCertificateError: version 5.7.1: HOMEPAGE: SSL cert error: HTTPSConnectionPool(host='xrootd.slac.stanford.edu', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1004)'))): https://xrootd.slac.stanford.edu/