Seems to be looking for OS 10.13.5 machines but there are none.
Guessing it should have been changed to 10.13.6 when machines got upgraded.
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mac%20FYI%20dEQP%20Release%20AMD/26928
15. angle_deqp_egl_gl_tests on ATI GPU on Mac Retina on Mac-10.13.5 Run on OS: 'Mac-10.13.5'
some shards did not complete: 0, 1, 2, 3
swarming.summary
Merge script log
step_metadata
shard #0 expired, not enough capacity
shard #1 expired, not enough capacity
shard #2 expired, not enough capacity
shard #3 expired, not enough capacity
missing shard #0
missing shard #1
missing shard #2
missing shard #3
Comment 1 by bugdroid1@chromium.org
, Sep 7