gh-129363: Change regrtest sequential mode output

[vstinner]

Always display the previous test, even if it passed in less than 30 seconds.

Example, before:

Example, after with colors:

• Issue: python -m test color print with and without -j #129363

[vstinner]

@hugovk: Here is a different proposition, alternative to #129476.

[hugovk]

Hmm, I'm not so keen that we get the result printed after we print the next test has started. It's a little confusing to have them on different lines.

From #129476 (comment):

Shall we take inspiration from pytest, which first prints the (uncoloured) name of the test, and then appends the coloured result?

Currently, when a test fails, it's output is written directly. So we cannot just add "passed" or "failed" after running a test.

Example (I added a bug to test_os):

0:00:00 load avg: 0.41 [1/1] test_os
test test_os failed -- Traceback (most recent call last):
  File "/home/vstinner/python/main/Lib/test/test_os.py", line 188, in test_access
    x
NameError: name 'x' is not defined

0:00:00 load avg: 0.41 [1/1/1] test_os failed (1 error)

Would something like this be possible?

• Show the green "passed" immediately after
• If there's a failure, we get some red showing the failure, and then the failure details
• If needed, we could add a red summary line after the failure details, before the next test starts

This minimises the amount of duplication, and we don't mix different tests on the same line, and it's all synchronous.

[vstinner]

@hugovk: That's more complicated to implement since regrtest is designed in a way that errors are written after "test_asyncio". Errors are written immediately, there is no buffer. So it's not easy to add "passed" or "failed" afterwards.

[hugovk]

Okay, then of these two, I prefer #129476 -- I find the extra lines clearer than the "zigzag" here.

Shall we go for #129476?

And hopefully Thomas will finish his update at a sprint one day :)

[vstinner]

Okay, then of these two, I prefer #129476 -- I find the extra lines clearer than the "zigzag" here.

Ok, I reopened the PR #129476.

[vstinner]

I close this PR. The other PR was merged instead: #129476