bz2 would use a dedicated exception for data error

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-09-05.10:26:14.525>
labels = ['extension-modules', 'type-feature', '3.10']
title = 'bz2 would use a dedicated exception for data error'
updated_at = <Date 2020-09-12.03:19:17.385>
user = 'https://github.com/mgorny'

bugs.python.org fields:

activity = <Date 2020-09-12.03:19:17.385>
actor = 'mgorny'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Extension Modules']
creation = <Date 2020-09-05.10:26:14.525>
creator = 'mgorny'
dependencies = []
files = []
hgrepos = []
issue_num = 41725
keywords = []
message_count = 3.0
messages = ['376427', '376744', '376769']
nosy_count = 3.0
nosy_names = ['terry.reedy', 'mgorny', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue41725'
versions = ['Python 3.10']