IDLE editor file minor refactoring

GitHub fields:

assignee = 'https://github.com/terryjreedy'
closed_at = None
created_at = <Date 2021-04-20.16:15:23.437>
labels = ['expert-IDLE', '3.8', '3.9', '3.10']
title = 'IDLE editor file minor refactoring'
updated_at = <Date 2021-04-23.21:23:39.532>
user = 'https://github.com/E-Paine'

bugs.python.org fields:

activity = <Date 2021-04-23.21:23:39.532>
actor = 'epaine'
assignee = 'terry.reedy'
closed = False
closed_date = None
closer = None
components = ['IDLE']
creation = <Date 2021-04-20.16:15:23.437>
creator = 'epaine'
dependencies = []
files = []
hgrepos = []
issue_num = 43894
keywords = ['patch']
message_count = 4.0
messages = ['391449', '391727', '391735', '391736']
nosy_count = 3.0
nosy_names = ['terry.reedy', 'eric.araujo', 'epaine']
pr_nums = ['25485']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue43894'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']