YamlException.ToString hiddes stack track

[rosieks]

The YamlException class overrides the ToString method so that it only displays parsing error of the exception. Typically, in such cases, exceptions also include the exception class name and the stack trace. This change makes debugging more challenging, especially if the developer is unaware that the ToString method’s behavior is non-standard.

[liskin]

Not only does this make debugging challenging, it seriously affects this use-case:
https://github.com/aaubry/YamlDotNet/blob/master/YamlDotNet.Samples/ValidatingDuringDeserialization.cs

Exceptions thrown during validation are completely hidden and not exposed to the user. Any chance #1000 could be merged? (I added a review comment as I believe the PR can be simplified a lot. I'm happy to make those changes myself if @rosieks doesn't.)

[EdwardCooke]

When I get some time to really spend on this project I'll merge it in. One thing I would like to see is that become an option in the builders. Suddenly including the stack trace could be a disruptive change to people. Hopefully without changing any public method signatures.

[rosieks]

How would you see that working?
I think the fixed version should actually be the default behavior. That would mean that after updating, people would need to touch their code anyway if they wanted to keep the previous behavior. Looking at when such a problem might occur, it seems limited to cases where someone is interpreting the output of ToString(). That’s generally an uncommon practice, since most people expect a stack trace there.