Use AsyncMock with python 3.8 instead of asynctest

tests/test_api/test_client/test_base_bot.py

@@ -1,12 +1,14 @@
-import copy
-
 import pytest
-from asynctest import CoroutineMock, patch
 
 from aiogram.api.client.base import BaseBot
 from aiogram.api.client.session.aiohttp import AiohttpSession
 from aiogram.api.methods import GetMe
 
+try:
+    from asynctest import CoroutineMock, patch
+except ImportError:
+    from unittest.mock import AsyncMock as CoroutineMock, patch
+
 
 class TestBaseBot:
     def test_init(self):

tests/test_api/test_client/test_session/test_aiohttp_session.py

@@ -4,12 +4,16 @@ from typing import AsyncContextManager
 import aiohttp
 import pytest
 from aresponses import ResponsesMockServer
-from asynctest import CoroutineMock, patch
 
 from aiogram.api.client.session.aiohttp import AiohttpSession
 from aiogram.api.methods import Request, TelegramMethod
 from aiogram.api.types import InputFile
 
+try:
+    from asynctest import CoroutineMock, patch
+except ImportError:
+    from unittest.mock import AsyncMock as CoroutineMock, patch
+
 
 class BareInputFile(InputFile):
     async def read(self, chunk_size: int):

tests/test_api/test_client/test_session/test_base_session.py

@@ -2,13 +2,17 @@ import datetime
 from typing import AsyncContextManager
 
 import pytest
-from asynctest import CoroutineMock, patch
 
 from aiogram.api.client.session.base import BaseSession, T
 from aiogram.api.client.telegram import PRODUCTION, TelegramAPIServer
 from aiogram.api.methods import GetMe, Response, TelegramMethod
 from aiogram.utils.mixins import DataMixin
 
+try:
+    from asynctest import CoroutineMock, patch
+except ImportError:
+    from unittest.mock import AsyncMock as CoroutineMock, patch
+
 
 class CustomSession(BaseSession):
     async def close(self):