[FIX] make changes processing code more obvious

beesdoo_shift_swap/models/planning.py

@@ -43,14 +43,13 @@ def _prepare_task_day(self):
 
         swap_subscription_done = []
         for shift in shifts:
-            for rec in list(changes):
+            to_process = changes
+            changes = []
+            for rec in to_process:
                 shift, swap_subscription_done, done = rec.update_shift_data(
                     shift, swap_subscription_done
                 )
-                if done:
-                    # You're not supposed to remove items from a list while
-                    # looping over it. We circumvent this problem by looping
-                    # over a copy of the list, which will not be affected.
-                    changes.remove(rec)
+                if not done:
+                    changes.append(rec)
 
         return shifts