Exceptions thrown by generators aren't caught

[gfredericks]

Exceptions in generators should probably result in a test failure, and maybe even shrink to find the smallest [seed size] that throws an exception.

[gfredericks]

It's worth noting that an exceptional generator when using clojure.test results in an error being reported, which I think is the desired behavior.

[reiddraper]

I think for now I'm going to close this as 'don't do that', but happy to revisit if others feel differently.