Deprecate is_allowed_by_hierarchy() core util (#4435)

redbot/core/utils/mod.py

@@ -1,4 +1,5 @@
 import asyncio
+import warnings
 from datetime import timedelta
 from typing import List, Iterable, Union, TYPE_CHECKING, Dict
 
@@ -92,6 +93,12 @@ def get_audit_reason(author: discord.Member, reason: str = None):
 async def is_allowed_by_hierarchy(
     bot: "Red", settings: "Config", guild: discord.Guild, mod: discord.Member, user: discord.Member
 ):
+    warnings.warn(
+        "`is_allowed_by_hierarchy()` is deprecated since Red 3.4.1"
+        " and will be removed in the first minor release after 2020-11-31.",
+        DeprecationWarning,
+        stacklevel=2,
+    )
     if not await settings.guild(guild).respect_hierarchy():
         return True
     is_special = mod == guild.owner or await bot.is_owner(mod)