Tempest silently hides crash due to OOM

I was running the full Tempest suite via Rally. It looked like the suite passed successfully:

[...]
2020-07-09 10:48:32.672 16426 INFO default [-] {0} tempest.api.identity.admin.v3.test_list_users.UsersV3TestJSON.test_list_users_with_not_enabled ... success [0.142s]
2020-07-09 10:49:22.303 16426 INFO rally.task.context [-] Verification a73cc1fa-aa39-4427-8e3a-33ea223c2a4f | Context testr@default cleanup() started
2020-07-09 10:49:22.303 16426 INFO rally.task.context [-] Verification a73cc1fa-aa39-4427-8e3a-33ea223c2a4f | Context testr@default cleanup() finished in 0.82 msec
2020-07-09 10:49:22.304 16426 INFO rally.task.context [-] Verification a73cc1fa-aa39-4427-8e3a-33ea223c2a4f | Context tempest@default cleanup() started
2020-07-09 10:49:32.420 16426 INFO rally.task.context [-] Verification a73cc1fa-aa39-4427-8e3a-33ea223c2a4f | Context tempest@default cleanup() finished in 10.12 sec
2020-07-09 10:49:32.467 16426 INFO rally.api [-] Verification (UUID=6160b3bb-7d54-4e6f-a360-c185ae578135) has been successfully finished for deployment 'production' (UUID=206669da-6147-4
29e-b92c-c3ec049974e5)!

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Totals
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Ran: 1558 tests in 3693.127 sec.
 - Success: 579
 - Skipped: 138
 - Expected failures: 0
 - Unexpected success: 0
 - Failures: 0

Using verification (UUID=6160b3bb-7d54-4e6f-a360-c185ae578135) as the default verification for the future operations.

The HTML report matches these numbers: 579 tests in "success" status and 138 in "skipped" status.

However, if you look more closely at the test numbers, they don't add up at all: there are 841 tests missing! With `rally verify show 6160b3bb-7d54-4e6f-a360-c185ae578135` I was able to see that the 841 missing tests were in `init` status.

I found the reason tests stopped running at that point: there was an OOM which killed a python process:

[Thu Jul 9 10:49:20 2020] Out of memory: Killed process 16431 (python) total-vm:2074092kB, anon-rss:1509788kB, file-rss:0kB, shmem-rss:0kB, UID:1000
[Thu Jul 9 10:49:20 2020] oom_reaper: reaped process 16431 (python), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB

Unfortunately tempest hides this failure and makes it look like the test suite completed successfully.