Drop support of Tcl/Tk older than 8.5.12

[serhiy-storchaka]

BPO	46996
Nosy	@terryjreedy, @ronaldoussoren, @serhiy-storchaka, @erlend-aasland, @E-Paine
PRs	bpo-46996: Remove support of Tcl/Tk < 8.5.12 #31839 gh-91152: IDLE: Drop workarounds for old Tk versions #31962

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2022-03-17.17:32:23.273>
created_at = <Date 2022-03-12.16:03:38.426>
labels = ['tests', '3.11', 'type-feature', 'expert-tkinter', 'library']
title = 'Drop support of Tcl/Tk older than 8.5.12'
updated_at = <Date 2022-03-19.15:14:25.332>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2022-03-19.15:14:25.332>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2022-03-17.17:32:23.273>
closer = 'terry.reedy'
components = ['Library (Lib)', 'Tests', 'Tkinter']
creation = <Date 2022-03-12.16:03:38.426>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 46996
keywords = ['patch']
message_count = 9.0
messages = ['414999', '415394', '415395', '415397', '415420', '415423', '415434', '415472', '415555']
nosy_count = 5.0
nosy_names = ['terry.reedy', 'ronaldoussoren', 'serhiy.storchaka', 'erlendaasland', 'epaine']
pr_nums = ['31839', '31962']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue46996'
versions = ['Python 3.11']

[serhiy-storchaka]

In bpo-45979 E. Paine suggested to drop support of Tcl/Tk older than 8.5.12 (8.5.12 was released on 2012-07-27 and 8.6.0 on 2012-12-20). Tkinter tests contain workarounds and special cases for older versions of Tcl/Tk, many of them can be removed. Also some Python and C code of tkinter can be simplified.

[ronaldoussoren]

One consideration is support for older LTS distributions of Linux, RHEL/Centos 7 appears to ship with Tcl/Tk 8.5.

The system install of Tcl/Tk on macOS is also 8.5, but that variant has too many bugs to try to support it.

[serhiy-storchaka]

8.5.12 will be 10 years old at the time of releasing 3.11.

We can relax the requirements for 8.5.x, so the code can be build with older versions, but some tests will fail because we removed workarounds for differences in behavior in older versions from tests.

The LTS distributions can also provide their own patches which relax the requirements.

[serhiy-storchaka]

New changeset c2e3c06 by Serhiy Storchaka in branch 'main':
bpo-46996: Remove support of Tcl/Tk < 8.5.12 (GH-31839)
c2e3c06