From the review:

This function is already unmanageably complex (and complexity checks disabled in the backport). Adding this single boolean parameter has expanded this function from ~120 lines to almost 160 and increases the mccabe cyclometric complexity of this function from 25 to 31 (where a target complexity is <10).

cpython main @ pip-run mccabe -- -m mccabe --min 14 Lib/configparser.py
940:4: 'RawConfigParser._read' 25
 cpython main @ gh pr checkout 117273
Switched to branch 'unnamed-section'
 cpython unnamed-section @ pip-run mccabe -- -m mccabe --min 14 Lib/configparser.py
961:4: 'RawConfigParser._read' 31

Originally posted by @jaraco in #117273 (comment)

Linked PRs

• gh-117348: Refactored RawConfigParser._read for simplicity and comprehensibility #117372
• gh-117348: restore import time performance of configparser #117703