copy.deepcopy can fail with unhelpful diagnostics

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2022-02-20.15:57:04.499>
labels = ['type-feature', 'library', '3.9']
title = 'copy.deepcopy can fail with unhelpful diagnostics'
updated_at = <Date 2022-02-20.15:57:04.499>
user = 'https://github.com/remdragon'

bugs.python.org fields:

activity = <Date 2022-02-20.15:57:04.499>
actor = 'remdragon'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2022-02-20.15:57:04.499>
creator = 'remdragon'
dependencies = []
files = []
hgrepos = []
issue_num = 46809
keywords = []
message_count = 1.0
messages = ['413594']
nosy_count = 1.0
nosy_names = ['remdragon']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue46809'
versions = ['Python 3.9']