Fixed AsyncMock issue in Python 3.7

Author: gkevinzheng

tests/unit/admin_overlay/test_async_consistency.py

@@ -16,6 +16,7 @@
 # try/except added for compatibility with python < 3.8
 try:
     from unittest import mock
+    from unittest.mock import AsyncMock  # pragma: NO COVER
 except ImportError:  # pragma: NO COVER
     import mock