Errors in VM code called from Nimscript is hidden

[Araq]

There is a mechanism called `getError` that is used for VM/native integration 
for `os.nim`:
    
    
    proc getError: string = builtin
    
    ...
      
      result.registerCallback "stdlib.system.getError",
        proc (a: VmArgs) = setResult(a, errorMsg)
    
    
    Run

You could use the existing `getError` or a similar mechanism to communiate 
errors between the native and the VM code.