Call sys.unraisablehook in the REPL when sys.excepthook is broken

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-02-06.20:55:56.550>
labels = ['3.10']
title = 'Call sys.unraisablehook in the REPL when sys.excepthook is broken'
updated_at = <Date 2021-02-15.16:58:07.957>
user = 'https://github.com/Julian'

bugs.python.org fields:

activity = <Date 2021-02-15.16:58:07.957>
actor = 'Julian2'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2021-02-06.20:55:56.550>
creator = 'Julian'
dependencies = []
files = []
hgrepos = []
issue_num = 43148
keywords = []
message_count = 3.0
messages = ['386569', '386703', '387026']
nosy_count = 4.0
nosy_names = ['vstinner', 'Carl.Friedrich.Bolz', 'Julian', 'Julian2']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue43148'
versions = ['Python 3.10']