autopurge: add some logging and lower the parallel purges

[david-caro]

Also my editor autoformatted the code.

[david-caro]

Example of run:

==> autopurge-hourly.err <==
Skipped '/workspace/user-config.py': owned by someone else.
2024-03-14 14:41:41,386 INFO     Starting hourly purge...
2024-03-14 14:41:45,595 INFO     Starting purge: Processing 1984 members for category К:Википедия:Страницы с ежечасно очищаемым кэшем
Sleeping for 5.5 seconds, 2024-03-14 14:41:45
2024-03-14 14:41:51,446 INFO         purged from 0 to 50
Sleeping for 9.5 seconds, 2024-03-14 14:41:51
2024-03-14 14:42:01,393 INFO         purged from 50 to 100
Sleeping for 9.7 seconds, 2024-03-14 14:42:01
2024-03-14 14:42:11,403 INFO         purged from 100 to 150
Sleeping for 9.7 seconds, 2024-03-14 14:42:11
2024-03-14 14:42:21,430 INFO         purged from 150 to 200
Sleeping for 9.7 seconds, 2024-03-14 14:42:21
2024-03-14 14:42:31,395 INFO         purged from 200 to 250
Sleeping for 9.7 seconds, 2024-03-14 14:42:31
2024-03-14 14:42:41,436 INFO         purged from 250 to 300
Sleeping for 9.7 seconds, 2024-03-14 14:42:41
2024-03-14 14:42:51,413 INFO         purged from 300 to 350
Sleeping for 9.7 seconds, 2024-03-14 14:42:51
2024-03-14 14:43:01,424 INFO         purged from 350 to 400
Sleeping for 9.7 seconds, 2024-03-14 14:43:01
2024-03-14 14:43:11,419 INFO         purged from 400 to 450
Sleeping for 9.7 seconds, 2024-03-14 14:43:11
2024-03-14 14:43:21,425 INFO         purged from 450 to 500
Sleeping for 9.7 seconds, 2024-03-14 14:43:21
2024-03-14 14:43:31,619 INFO         purged from 500 to 550
Sleeping for 9.5 seconds, 2024-03-14 14:43:31
2024-03-14 14:43:41,667 INFO         purged from 550 to 600
Sleeping for 9.4 seconds, 2024-03-14 14:43:41
2024-03-14 14:43:52,400 INFO         purged from 600 to 650
Sleeping for 8.7 seconds, 2024-03-14 14:43:52
2024-03-14 14:44:08,300 INFO         purged from 650 to 700
2024-03-14 14:44:19,944 INFO         purged from 700 to 750
2024-03-14 14:44:27,351 INFO         purged from 750 to 800
Sleeping for 3.8 seconds, 2024-03-14 14:44:27
2024-03-14 14:44:38,654 INFO         purged from 800 to 850
2024-03-14 14:44:47,787 INFO         purged from 850 to 900
Sleeping for 3.3 seconds, 2024-03-14 14:44:47
2024-03-14 14:44:58,198 INFO         purged from 900 to 950
2024-03-14 14:45:06,855 INFO         purged from 950 to 1000
Sleeping for 4.3 seconds, 2024-03-14 14:45:06
2024-03-14 14:45:16,147 INFO         purged from 1000 to 1050
Sleeping for 5.0 seconds, 2024-03-14 14:45:16
2024-03-14 14:45:29,565 INFO         purged from 1050 to 1100
2024-03-14 14:45:37,046 INFO         purged from 1100 to 1150
Sleeping for 4.1 seconds, 2024-03-14 14:45:37
2024-03-14 14:45:50,702 INFO         purged from 1150 to 1200
2024-03-14 14:45:57,665 INFO         purged from 1200 to 1250
Sleeping for 3.5 seconds, 2024-03-14 14:45:57
2024-03-14 14:46:10,185 INFO         purged from 1250 to 1300
2024-03-14 14:46:16,272 INFO         purged from 1300 to 1350
Sleeping for 4.8 seconds, 2024-03-14 14:46:16
2024-03-14 14:46:26,017 INFO         purged from 1350 to 1400
Sleeping for 5.1 seconds, 2024-03-14 14:46:26
2024-03-14 14:46:37,922 INFO         purged from 1400 to 1450
Sleeping for 3.2 seconds, 2024-03-14 14:46:37
2024-03-14 14:46:46,054 INFO         purged from 1450 to 1500
Sleeping for 5.1 seconds, 2024-03-14 14:46:46
2024-03-14 14:46:56,418 INFO         purged from 1500 to 1550
Sleeping for 4.7 seconds, 2024-03-14 14:46:56
2024-03-14 14:47:05,789 INFO         purged from 1550 to 1600
Sleeping for 5.3 seconds, 2024-03-14 14:47:05
2024-03-14 14:47:16,650 INFO         purged from 1600 to 1650
Sleeping for 4.5 seconds, 2024-03-14 14:47:16
2024-03-14 14:47:27,181 INFO         purged from 1650 to 1700
Sleeping for 3.9 seconds, 2024-03-14 14:47:27
2024-03-14 14:47:38,592 INFO         purged from 1700 to 1750
2024-03-14 14:47:49,445 INFO         purged from 1750 to 1800
2024-03-14 14:47:59,386 INFO         purged from 1800 to 1850
2024-03-14 14:48:12,402 INFO         purged from 1850 to 1900
2024-03-14 14:48:18,435 INFO         purged from 1900 to 1950
Sleeping for 4.0 seconds, 2024-03-14 14:48:18
2024-03-14 14:48:28,720 INFO         purged from 1950 to 2000
2024-03-14 14:48:28,721 INFO     Purged 1984 members
2024-03-14 14:48:28,725 INFO     Finished

I think that the high parallel rate was what was making it fail, making it go a bit slower seems to make it run without issues.