bpo-4080: unittest durations

[giampaolo]

Adds cmdline option to show unit-tests durations + summary of the slowest ones, see https://bugs.python.org/issue4080.

Top 5 slowest ones:

$ ./python -m unittest Lib.test.test_ftplib --durations=5 
..........................................s.............................................
Slowest test durations
----------------------------------------------------------------------
0.203s     test_with_statement (Lib.test.test_ftplib.TestFTPClass)
0.204s     test_retrbinary_rest (Lib.test.test_ftplib.TestTLS_FTPClassMixin)
0.214s     test_with_statement (Lib.test.test_ftplib.TestTLS_FTPClassMixin)
0.881s     test_mlsd (Lib.test.test_ftplib.TestFTPClass)
1.162s     test_mlsd (Lib.test.test_ftplib.TestTLS_FTPClassMixin)

----------------------------------------------------------------------
Ran 88 tests in 5.264s

OK (skipped=1)

All + individual elapsed time:

$ ./python -m unittest Lib.test.test_ftplib --durations=0 -v
test_abort (Lib.test.test_ftplib.TestFTPClass) ... [0.002s] ok
test_all_errors (Lib.test.test_ftplib.TestFTPClass) ... [0.001s] ok
test_cwd (Lib.test.test_ftplib.TestFTPClass) ... [0.001s] ok
test_delete (Lib.test.test_ftplib.TestFTPClass) ... [0.001s] ok
test_dir (Lib.test.test_ftplib.TestFTPClass) ... [0.041s] ok
test_mlsd (Lib.test.test_ftplib.TestFTPClass) ... [0.880s] ok
test_nlst (Lib.test.test_ftplib.TestFTPClass) ... [0.092s] ok
test_parse257 (Lib.test.test_ftplib.TestFTPClass) ... [0.002s] ok
...

Slowest test durations
----------------------------------------------------------------------
0.000s     test__all__ (Lib.test.test_ftplib.MiscTestCase)
0.002s     test_pwd (Lib.test.test_ftplib.TestFTPClass)
....
0.140s     test_storbinary_rest (Lib.test.test_ftplib.TestTLS_FTPClassMixin)
0.148s     test_data_connection (Lib.test.test_ftplib.TestTLS_FTPClass)
0.154s     test_storlines (Lib.test.test_ftplib.TestTLS_FTPClassMixin)
0.175s     test_retrbinary_rest (Lib.test.test_ftplib.TestTLS_FTPClassMixin)
0.204s     test_with_statement (Lib.test.test_ftplib.TestFTPClass)
0.208s     test_with_statement (Lib.test.test_ftplib.TestTLS_FTPClassMixin)
0.880s     test_mlsd (Lib.test.test_ftplib.TestFTPClass)
1.281s     test_mlsd (Lib.test.test_ftplib.TestTLS_FTPClassMixin)

----------------------------------------------------------------------
Ran 88 tests in 5.396s

OK (skipped=1)

https://bugs.python.org/issue4080

[giampaolo]

@LiteApplication thanks for approving. Merging.

[eggplants]

@giampaolo @LiteApplication doesn't appear to be a regular Python reviewer, is it no problem to merge?

[terryjreedy]

Hidden buildbot failure was for test_asyncio. I presume unrelated since random test_asyncio failures are unfortunately routine.

[giampaolo]

I created #103209 to address @gpshead's post-merge comments to this PR.

[giampaolo]

@eggplants wrote:

@giampaolo @LiteApplication doesn't appear to be a regular Python reviewer, is it no problem to merge?

Sorry, I didn't realize that. This was an old PR that unfortunately never received much attention, so it stayed idle for a long time and I occasionally updated it to fix merge conflicts. When I finally saw an approval I was just happy to see it and merged it without further checking. FWIW, I went through these changes multiple times over the last 4 years: I'm confident that the changes introduced in here are OK and are fully retro compatible (this probably was the most sensitive part to consider).

[eggplants]

Anyway, I am glad this feature has finally been merged. Thank you @giampaolo -san.

[giampaolo]

Here's a nose issue related to this PR's retro-compatibility: nose-devs/nose2#569.
nose extended TestCase class without defining the new addDuration method. Python 3.12 emitted a warning but it didn't crash.