remove deprecated helper method

change alter_cache to update_cache to better match what the method does (+1 squashed commits)

Squashed commits:

[23d61e14d] fix test

evennia/contrib/rpg/buffs/buff.py

@@ -234,8 +234,8 @@ class BaseBuff:
         self.start = time.time()
         self.handler.buffcache[self.buffkey]["start"] = time.time()
 
-    def alter_cache(self, to_cache: dict):
+    def update_cache(self, to_cache: dict):
-        """Alters this buff's cache, both internally (this instance) and on the handler's buff cache.
+        """Updates this buff's cache using the given values, both internally (this instance) and on the handler.
 
         Args:
             to_cache:   The dictionary of values you want to add to the cache"""
@@ -930,16 +930,6 @@ class BuffHandler:
                 )
         return
 
-    def set_duration(self, key, value):
-        """Sets the duration of the specified buff.
-
-        Args:
-            key:    The key of the buff whose duration you want to set
-            value:  The value you want the new duration to be"""
-        if key in self.buffcache.keys():
-            self.buffcache[key]["duration"] = value
-        return
-
     def view(self, to_filter=None) -> dict:
         """Returns a buff flavor text as a dictionary of tuples in the format {key: (name, flavor)}. Common use for this is a buff readout of some kind.
 

evennia/contrib/rpg/buffs/tests.py

@@ -368,7 +368,7 @@ class TestBuffsAndHandler(EvenniaTest):
         _instance.at_tick()
         self.assertTrue(self.testobj.db.ticktest)
         # test duration modification and cleanup
-        handler.set_duration("ttib", 0)
+        _instance.duration = 0
         self.assertEqual(handler.get("ttib").duration, 0)
         handler.cleanup()
         self.assertFalse(handler.get("ttib"), None)