IDLE reformat tests fail in presence of non-default FormatParagraph setting

[rhettinger]

BPO	21284
Nosy	@rhettinger, @terryjreedy

^{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 = 'https://github.com/terryjreedy'
closed_at = <Date 2014-04-22.05:13:27.761>
created_at = <Date 2014-04-17.15:19:38.994>
labels = ['easy', 'expert-IDLE', 'type-bug']
title = 'IDLE reformat tests fail in presence of non-default FormatParagraph setting'
updated_at = <Date 2014-04-22.05:13:27.760>
user = 'https://github.com/rhettinger'

bugs.python.org fields:

activity = <Date 2014-04-22.05:13:27.760>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = True
closed_date = <Date 2014-04-22.05:13:27.761>
closer = 'terry.reedy'
components = ['IDLE']
creation = <Date 2014-04-17.15:19:38.994>
creator = 'rhettinger'
dependencies = []
files = []
hgrepos = []
issue_num = 21284
keywords = ['easy']
message_count = 3.0
messages = ['216695', '216819', '216985']
nosy_count = 3.0
nosy_names = ['rhettinger', 'terry.reedy', 'python-dev']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue21284'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5']

[rhettinger]

When a user sets FormatParagraph to anything other than 70,
test_idle.py has 4 failing tests:

test_comment_block (idlelib.idle_test.test_formatparagraph.FormatEventTest) ... FAIL
test_long_line (idlelib.idle_test.test_formatparagraph.FormatEventTest) ... FAIL
test_multiple_lines (idlelib.idle_test.test_formatparagraph.FormatEventTest) ... FAIL
test_short_line (idlelib.idle_test.test_formatparagraph.FormatEventTest) ... FAIL

The solution is to make these tests setup by:

1. save the user's default configuration
2. set the paragraph reformat width to 70
   and tear-down by:
3. restoring the user's default configuration

[terryjreedy]

I noticed the same while working on bpo-21139 and posted there a patch, 21139-34-fpe.diff, that adds a limit parameter to .format_paragraph_event. Test could then specify a width for each test without touching the user configuration. Different tests could use different widths. An explicit width is already used for testing the implementaton functions called by this method.

[python-dev]

New changeset 4ff2c0a637cf by Terry Jan Reedy in branch '2.7':
bpo-21284: Idle: make test_formatparagraph pass even when a user changes the
http://hg.python.org/cpython/rev/4ff2c0a637cf

New changeset fe067339af80 by Terry Jan Reedy in branch '3.4':
bpo-21284: Idle: make test_formatparagraph pass even when a user changes the
http://hg.python.org/cpython/rev/fe067339af80