Show an error message if a shell command is too long to execute

[Taitava]

When creating tests for {{file_content}} and {{note_content}} variables, I noticed that at least Windows PowerShell has some (unknown) max limit for how long a shell command can be. This resulted in an exception in JavaScript's console, i.e. not as a visible error message.

I'll make the SC plugin to notice this exception and show it clearly to users.