preserve environment list over experiment changes

detect NewExperiment or FinishExperiment and restore
the previous environment if some of them are needed
for the current running frappy/sea servers

devices.py

@@ -182,8 +182,17 @@ class FrappyConfig(Device):
         before_check = before_change = prev_shown = None
         cnt = 0
         self._back_to_normal = None
+        current_exp = id(session.experiment.propinfo)
+        exp_changed = False
+        envlist = []
         while not self._shutdown_event.wait(1):
             busy = session.daemon_device._controller.status >= 0
+            if id(session.experiment.propinfo) != current_exp:
+                # NewExperiment or FinishExperiment was called
+                current_exp = id(session.experiment.propinfo)
+                exp_changed = True
+            elif not exp_changed:
+                envlist = session.experiment.envlist
             if self._restarting or (busy and cnt < 10):
                 # do not check while restarting and check only every 10 sec when busy
                 cnt += 1
@@ -197,6 +206,17 @@ class FrappyConfig(Device):
                 self._back_to_normal = None
             cnt = 0
             need_change, changes, fm = to_consider = self.to_consider()
+            if exp_changed:
+                exp_changed = False
+                needed = set(self.needed_envalias()[0])
+                if needed == needed.intersection(envlist) and not session.experiment.envlist:
+                    # restore envlist from previous experiment, as it was cleared by New/FinishExperiment
+                    session.experiment.setEnvironment(envlist)
+                    session.log.info('keep environment from previous experiment: %s', ', '.join(envlist))
+                    continue
+                # trigger output of proposed SE change
+                prev_shown = None
+                need_change = True
             if fm.state == before_change:
                 continue
             if not need_change:
@@ -383,7 +403,7 @@ class FrappyConfig(Device):
         - frappy('restart')         # restart all frappy servers
         - frappy('reconnect')       # reconnect to running frappy servers
         """
-        self._back_to_normal = None  # reset 'back to normal' machanism
+        self._back_to_normal = None  # reset 'back to normal' mechanism
         stickarg = stick
 
         need_change, changes, fm = to_consider = self.to_consider()
@@ -650,7 +670,7 @@ class FrappyConfig(Device):
         if anew:
             return f"aliases {', '.join(anew)} should change"
         if removed:
-            return f"aliases {', '.join(anew)} should be removed"
+            return f"aliases {', '.join(removed)} should be removed"
         return None
 
     def set_envalias(self):