Error with https://doubleSlash.de

exception = HTTPSConnectionPool(host='doubleslash.de', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLCertVerificationError(1, "[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: Hostname mismatch, certificate is not valid for 'doubleslash.de'. (_ssl.c:992)")))