Usability improvements for Python DSL

Based on current experience of Python DSL, which we understand its in very early and experimental state, we need to have following addressed as a part of Python DSL support (assume similar will be applicable for Scala DSL)

1. Generate descriptive error message point to exact error instead of multiple stack traces.
2. Line # and/or statement causing error from the script.
3. Explain to reflect HOPS etc properly.
Last time we observed that within a for loop it generates HOPS for every iteration, instead of once.