src/Pure/System/process_result.scala

   err_lines: List[String] = Nil,
   timeout: Option[Time] = None)
 {
   def out: String = cat_lines(out_lines)
   def err: String = cat_lines(err_lines)
+  def error(s: String): Process_Result = copy(err_lines = err_lines ::: List(s))
 
-  def error(s: String, err_rc: Int = 0): Process_Result =
-    copy(err_lines = err_lines ::: List(s), rc = rc max err_rc)
-
-  def set_timeout(t: Time): Process_Result = copy(timeout = Some(t))
+  def set_timeout(t: Time): Process_Result = copy(rc = 1, timeout = Some(t))
 
   def ok: Boolean = rc == 0
   def interrupted: Boolean = rc == Exn.Interrupt.return_code
 
   def check: Process_Result =