fix new statemachine with ips magfield

+ add on_error, on_restart etc. to states.py
+ add n_retry argument to mercury change/multichange

secop/states.py

@@ -118,12 +118,32 @@ class HasStates:
                 self.setFastPoll(False)
         self.read_status()
 
+    def on_cleanup(self, sm):
+        if isinstance(sm.cleanup_reason, Exception):
+            return self.on_error(sm)
+        if isinstance(sm.cleanup_reason, Start):
+            return self.on_restart(sm)
+        if isinstance(sm.cleanup_reason, Stop):
+            return self.on_stop(sm)
+        self.log.error('bad cleanup reason %r', sm.cleanup_reason)
+
+    def on_error(self, sm):
+        self.log.error('handle error %r', sm.cleanup_reason)
+        self.final_status(ERROR, repr(sm.cleanup_reason))
+        return None
+
+    def on_restart(self, sm):
+        return None
+
+    def on_stop(self, sm):
+        return None
+
     def start_machine(self, statefunc, fast_poll=True, **kwds):
         sm = self._state_machine
         sm.status = self.get_status(statefunc, BUSY)
         if sm.statefunc:
             sm.status = sm.status[0], 'restarting'
-        sm.start(statefunc, **kwds)
+        sm.start(statefunc, cleanup=kwds.pop('cleanup', self.on_cleanup), **kwds)
         self.read_status()
         if fast_poll:
             sm.reset_fast_poll = True