job.py: Modify retry messages to be FAIL

This adjusts the message handler for the child processes to no longer
override the message type.

This also removes the ability for unhandled non BstError exceptions to
retry.

buildstream/_scheduler/jobs/job.py

@@ -430,7 +430,8 @@ class Job():
                 self.message(MessageType.BUG, self.action_name,
                              elapsed=elapsed, detail=detail,
                              logfile=filename)
-                self._child_shutdown(RC_FAIL)
+                # Unhandled exceptions should permenantly fail
+                self._child_shutdown(RC_PERM_FAIL)
 
             else:
                 # No exception occurred in the action
@@ -509,11 +510,6 @@ class Job():
         message.action_name = self.action_name
         message.task_id = self._task_id
 
-        if (message.message_type == MessageType.FAIL and
-                self._tries <= self._max_retries and self._retry_flag):
-            # Job will be retried, display failures as warnings in the frontend
-            message.message_type = MessageType.WARN
-
         # Send to frontend if appropriate
         if context.silent_messages() and (message.message_type not in unconditional_messages):
             return