Feature request: Better error output from haskell cells

[aneilmac]

Overview

In xeus-haskell, when there is an error in a cell, the message Parse error: unable to parse snippet appears.

This makes diagnosis difficult for the user, as there is no context as to what caused the error. It would be useful if a more detailed error message could be provided, ideally the same error message which MicroHS would display when compiling. This would help users debug when writing a xeus-haskell notebook.

Example

A simple example is how unknown variables are currently treated.

Current behaviour

undeclaredVar
> Parse error: unable to parse snippet

Idealized behaviour

undeclaredVar
> error: Variable not in scope: `undeclaredVar`