Suppress exception response message

[dmfigol]

Currently exception messages are extremely big.
I propose suppress exception response sent from Spark server, leaving only necessary error message by default. Response could be still accessed as an exception attribute.

[cmlccie]

Some people like them. 😎

...but I agree they can be lengthy. I have had another recent request to enhance the errors. I'll see what I can do to make these a little cleaner.

[cmlccie]

@dmfigol I have released this enhancement in v1.1. Let me know if you have any feedback on the simplified error messages.