Spurious error when running fedora job (the change in the MR was only on documentation)

Job #87321473 failed for 01ff0177:

[00:00:00][fd215cab][build:import-dev.bst                ] SUCCESS test/import-dev/fd215cab-build.10679.log
Process Process-834:
Traceback (most recent call last):
  File "/usr/lib64/python3.6/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib64/python3.6/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "/builds/BuildStream/buildstream/dist/buildstream/buildstream/_scheduler/jobs/job.py", line 437, in _child_action
    self._queue.put(Envelope('child_data', self.child_process_data()))
  File "/builds/BuildStream/buildstream/dist/buildstream/buildstream/_scheduler/jobs/elementjob.py", line 113, in child_process_data
    cache_size = self._element._get_artifact_cache().calculate_cache_size()
  File "/builds/BuildStream/buildstream/dist/buildstream/buildstream/_artifactcache/cascache.py", line 476, in calculate_cache_size
    self.cache_size = utils._get_dir_size(self.casdir)
  File "/builds/BuildStream/buildstream/dist/buildstream/buildstream/utils.py", line 572, in _get_dir_size
    return get_size(path)
  File "/builds/BuildStream/buildstream/dist/buildstream/buildstream/utils.py", line 568, in get_size
    total += get_size(f.path)
  File "/builds/BuildStream/buildstream/dist/buildstream/buildstream/utils.py", line 565, in get_size
    total += f.stat(follow_symlinks=False).st_size
FileNotFoundError: [Errno 2] No such file or directory: '/builds/BuildStream/buildstream/dist/buildstream/tmp/test_push_after_pull0/cache/artifacts/cas/tmp/tmph4th_esx'
Coverage.py warning: No data was collected. (no-data-collected)
Coverage.py warning: No data was collected. (no-data-collected)

BUG: Message handling out of sync, unable to retrieve failure message for element import element at import-bin.bst [line 1 column 0]