Checker.Check() should return error, not (bool, string); would match Go idioms better

[Tv]

Right now, I need to do a lot of

  ..., err := something()
  if err != nil {
    return false, err.Error()
  }
  return true, ""

That is ugly for several reasons, including needing the empty string. Gocheck seems to be from an era where os.Error still existed (http://labix.org/gocheck shows os.Errno in example). Check() could just return a single err, and nil would mean success.