code: def compact_error(err):
    
    def err2(e):
      if isinstance(e, exceptions.EvaluationError) and e.inner:
        message, i = err2(e.inner)
        if i == 1:
          return ', '.join([e.args[0], str(e.inner)]), i + 1
        else:
          return message, i + 1
      else:
        return str(e), 1
    return err2(err)[0]
docs: Return the the last 2 error messages from an error stack.
  
    These error messages turns out to be the most descriptive.