Error output for run_clingo, run_dlv, etc.

[sahil1105]

Maybe return it as a separate element so it can be displayed, especially useful for PWE-NB-Extension where you want to be able to see the error in the code you're trying to experiment with.

[sahil1105]

Once implemented, add a feature (or at least a feature request) in PWE-NB-Extension to utilize this in Jupyter magic functions.