Display process errors to the user to help with debugging (eg, wrong PATH)

Hey there, thanks for this plugin. I've found that in most cases it is very useful to display the process sterr back to the user to help them debug why a subprocess might fail. 

Without this change, I was receiving the following error: "Could not expose available tasks". This is a very generic error and I had no idea where to start to fix things. 

My proposed change will now show the user the output of stderr which, in most cases, will contain some useful information. 

What do you think?