Modify SAX/expat parsing to avoid fragmentation of already-tiny content chunks

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-03-19.18:39:18.829>
labels = ['expert-XML', '3.8', 'type-feature', '3.7', '3.9']
title = 'Modify SAX/expat parsing to avoid fragmentation of already-tiny content chunks'
updated_at = <Date 2021-03-19.18:39:18.829>
user = 'https://github.com/ridgerat'

bugs.python.org fields:

activity = <Date 2021-03-19.18:39:18.829>
actor = 'ridgerat1611'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['XML']
creation = <Date 2021-03-19.18:39:18.829>
creator = 'ridgerat1611'
dependencies = []
files = []
hgrepos = []
issue_num = 43560
keywords = []
message_count = 1.0
messages = ['389108']
nosy_count = 1.0
nosy_names = ['ridgerat1611']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue43560'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']