Exception in AsyncMock side_effect cases incorrect refcount

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-06-13.14:52:01.808>
labels = ['type-bug', '3.9', 'expert-asyncio']
title = 'Exception in AsyncMock side_effect cases incorrect refcount'
updated_at = <Date 2021-06-13.14:52:01.808>
user = 'https://github.com/Penlect'

bugs.python.org fields:

activity = <Date 2021-06-13.14:52:01.808>
actor = 'penlect'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['asyncio']
creation = <Date 2021-06-13.14:52:01.808>
creator = 'penlect'
dependencies = []
files = []
hgrepos = []
issue_num = 44410
keywords = []
message_count = 1.0
messages = ['395752']
nosy_count = 3.0
nosy_names = ['asvetlov', 'yselivanov', 'penlect']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue44410'
versions = ['Python 3.9']