A format run failed in this test:

https://evergreen.mongodb.com/task/wiredtiger_ubuntu2004_stress_tests_format_stress_sanitizer_test_4_6873ef7d0c3f3babc28cdc4a16cc302038e51334_21_11_01_00_02_08

The error message indicates that the process terminated when it received SIGKILL (signal 9).  

format.sh: job in /data/mci/6cef57a4e7d945bb8c74cb9d09794dfa/wiredtiger/test/format/RUNDIR.37 exited with status 137 for an unknown reason

I don't see anything in format.sh or related scripts that would generate SIGKILL.  So I speculate that perhaps we ran out of memory on the evergreen host and the oom_reaper killed this task.  Unfortunately, the artifacts don't include syslog output, which would show if this happened.

This test is running 8 copies of format with address sanitizing enabled.  So there is a lot of memory pressure, and WT-3445 may have increased the memory footprint of format.