test_idle fails on Devuan 5 Linux

[LeamHall]

Bug report

Bug description:

On Devuan 5, with this command in a build script:

./python -m test -uall -j0 > $test_file 2>&1

the following is logged:

0:10:21 load avg: 3.54 [229/469/2] test_idle failed (1 error)
test test_idle failed -- Traceback (most recent call last):
  File "/usr/local/src/forks/cpython/Lib/idlelib/idle_test/test_configdialog.py", line 452, in test_highlight_target_text_mouse
    click_it(start_index)
    ~~~~~~~~^^^^^^^^^^^^^
  File "/usr/local/src/forks/cpython/Lib/idlelib/idle_test/test_configdialog.py", line 436, in click_it
    x, y, dx, dy = hs.bbox(start)
    ^^^^^^^^^^^^
TypeError: cannot unpack non-iterable NoneType object

But this passes:

./python -m test -uall -j0 test_idle
Using random seed: 2055385424
0:00:00 load avg: 0.00 Run 1 test in parallel using 1 worker process
0:00:01 load avg: 0.00 [1/1] test_idle passed

== Tests result: SUCCESS ==

1 test OK.

Total duration: 1.8 sec
Total tests: run=283 skipped=81
Total test files: run=1/1
Result: SUCCESS

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-113903: Fix an IDLE configdialog test #113973
• [3.12] gh-113903: Fix an IDLE configdialog test (GH-113973) #113974
• [3.11] gh-113903: Fix an IDLE configdialog test (GH-113973) #113975

[terryjreedy]

test_idle is passing because gui tests are not run. Same command in repository on my older Windows PC, current main:

Total duration: 19.7 sec
Total tests: run=619 skipped=4

If I omit -uall, I get what you did.

In any case, hs.bbox(start) returns None only if the 'start' char is not visible, so I believe the font being used on your system must be such that the last line is not visible. You could immediately test this by moving copying lines 428-9 to above 436 and indenting to match and changing 1.0 to `start'. I will add a PR with this later.