Revert "Merge pull request #12" (#56)

This reverts commit 42c0a8d8a5.

discord/ext/commands/bot.py

@@ -43,7 +43,6 @@ from .context import Context
 from . import errors
 from .help import HelpCommand, DefaultHelpCommand
 from .cog import Cog
-from discord.utils import raise_expected_coro
 
 if TYPE_CHECKING:
     import importlib.machinery
@@ -425,9 +424,11 @@ class BotBase(GroupMixin):
         TypeError
             The coroutine passed is not actually a coroutine.
         """
-        return raise_expected_coro(
-            coro, 'The pre-invoke hook must be a coroutine.'
-        )
+        if not asyncio.iscoroutinefunction(coro):
+            raise TypeError('The pre-invoke hook must be a coroutine.')
+
+        self._before_invoke = coro
+        return coro
 
     def after_invoke(self, coro: CFT) -> CFT:
         r"""A decorator that registers a coroutine as a post-invoke hook.
@@ -456,10 +457,11 @@ class BotBase(GroupMixin):
         TypeError
             The coroutine passed is not actually a coroutine.
         """
-        return raise_expected_coro(
-            coro, 'The post-invoke hook must be a coroutine.'
-        )
+        if not asyncio.iscoroutinefunction(coro):
+            raise TypeError('The post-invoke hook must be a coroutine.')
 
+        self._after_invoke = coro
+        return coro
 
     # listener registration