Add more info to the DEPTH_ZERO_SELF_SIGNED_CERT error

[binarykitchen]

If you see the other ticket #4984 you will see that I needed a while to find out about which one certificate node was talking about.

Just a DEPTH_ZERO_SELF_SIGNED_CERT and a stack trace not pointing to the real origin of the cause aren't very helpful for locating the problem.

In my app I had multiple ssl files for different component.

For this feature request I suggest to print an error like this instead:
Error: Cannot verify self-signed certificate /path/to/xxx.crt because depth is zero.

Like that I know the path to the certificate, what the problem is and know what to do, i.E. disable SSL verification or prepend root issuer(s) into the crt file.

I'm sure this will reduce the number of questions or bug reports from others encountering the same issue.