sslutil: emit warning when no CA certificates loaded If no CA certificates are loaded, that is almost certainly a/the reason certificate verification fails when connecting to a server. The modern ssl module in Python 2.7.9+ provides an API to access the list of loaded CA certificates. This patch emits a warning on modern Python when certificate verification fails and there are no loaded CA certificates. There is no way to detect the number of loaded CA certificates unless the modern ssl module is present. Hence the differences in test output depending on whether modern ssl is available. It's worth noting that a test which specifies a CA file still renders this warning. That is because the certificate it is loading is a x509 client certificate and not a CA certificate. This test could be updated if anyone is so inclined.