obslog: add preliminary support for showing predecessors

This functionality is not yet used right now, but will be in the next patch.
7 jobs for topic/default/obslog-predecessors in 3 minutes and 41 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed doc #69073

00:01:24

passed flake8 #69067

00:00:26

manual pytype #69068
allowed to fail manual
failed tests-py2-cext #69069

00:03:22

failed tests-py2-pure #69070

00:03:19

failed tests-py3-cext #69071

00:03:41

failed tests-py3-pure #69072

00:03:20

 
Name Stage Failure
failed
tests-py3-pure Test
Failed test-evolve-progress.t: output changed
Failed test-evolve-public-content-divergent-corner-cases.t: output changed
Failed test-evolve-public-content-divergent-main.t: output changed
Failed test-evolve.t: output changed
Failed test-topic.t: output changed
Failed test-unstability-resolution-result.t: output changed
# Ran 191 tests, 0 skipped, 7 failed.
python hash seed: 668523605
ERROR: Job failed: exit code 1
failed
tests-py3-cext Test
Failed test-evolve-progress.t: output changed
Failed test-evolve-public-content-divergent-corner-cases.t: output changed
Failed test-evolve-public-content-divergent-main.t: output changed
Failed test-evolve.t: output changed
Failed test-topic.t: output changed
Failed test-unstability-resolution-result.t: output changed
# Ran 191 tests, 0 skipped, 7 failed.
python hash seed: 582416351
ERROR: Job failed: exit code 1
failed
tests-py2-pure Test
Failed test-evolve-progress.t: output changed
Failed test-evolve-public-content-divergent-corner-cases.t: output changed
Failed test-evolve-public-content-divergent-main.t: output changed
Failed test-evolve.t: output changed
Failed test-topic.t: output changed
Failed test-unstability-resolution-result.t: output changed
# Ran 191 tests, 0 skipped, 7 failed.
python hash seed: 3156239361
ERROR: Job failed: exit code 1
failed
tests-py2-cext Test
Failed test-evolve-progress.t: output changed
Failed test-evolve-public-content-divergent-corner-cases.t: output changed
Failed test-evolve-public-content-divergent-main.t: output changed
Failed test-evolve.t: output changed
Failed test-topic.t: output changed
Failed test-unstability-resolution-result.t: output changed
# Ran 191 tests, 0 skipped, 7 failed.
python hash seed: 2373840509
ERROR: Job failed: exit code 1