Use built-in test helpers on 3.8 (#34901)

tests/components/shell_command/test_init.py

@@ -5,15 +5,13 @@ import tempfile
 from typing import Tuple
 import unittest
 
-from asynctest import Mock, patch
-
 from homeassistant.components import shell_command
 from homeassistant.setup import setup_component
 
+from tests.async_mock import Mock, patch
 from tests.common import get_test_home_assistant
 
 
-@asyncio.coroutine
 def mock_process_creator(error: bool = False) -> asyncio.coroutine:
     """Mock a coroutine that creates a process when yielded."""