Since some days the unit test mediawiki-phpunit-hhvm fails with a IOError

17:59:23 INFO:zuul.Cloner:Loaded map containing 4 rules
17:59:23 INFO:zuul.CloneMapper:Workspace path set to: src
17:59:23 INFO:zuul.CloneMapper:Mapping projects to workspace...
17:59:23 INFO:zuul.CloneMapper: mediawiki/core -> src
17:59:23 INFO:zuul.CloneMapper: mediawiki/vendor -> src/vendor
17:59:23 DEBUG:zuul.CloneMapper:Checking overlap in destination directories...
17:59:23 INFO:zuul.CloneMapper:Expansion completed.
17:59:23 INFO:zuul.Cloner:Preparing 2 repositories
17:59:23 INFO:zuul.Cloner:Creating repo mediawiki/core from upstream https://gerrit.wikimedia.org/r/p/mediawiki/core
17:59:23 DEBUG:zuul.Repo:Updating repository src
17:59:26 DEBUG:zuul.Cloner:upstream repo has branch master
17:59:27 DEBUG:zuul.Cloner:Fetched ref refs/zuul/master/Z643afea06eef4f95af29e5475f871d71 from mediawiki/core
17:59:27 DEBUG:zuul.Repo:Checking out aa72c4e0d27430ad4cd7781b508e80b165f73a4c
17:59:27 Traceback (most recent call last):
17:59:27 File "/usr/local/bin/zuul-cloner", line 10, in <module>
17:59:27 sys.exit(main())
17:59:27 File "/usr/local/lib/python2.7/dist-packages/zuul/cmd/cloner.py", line 156, in main
17:59:27 cloner.main()
17:59:27 File "/usr/local/lib/python2.7/dist-packages/zuul/cmd/cloner.py", line 151, in main
17:59:27 cloner.execute()
17:59:27 File "/usr/local/lib/python2.7/dist-packages/zuul/lib/cloner.py", line 66, in execute
17:59:27 self.prepareRepo(project, dest)
17:59:27 File "/usr/local/lib/python2.7/dist-packages/zuul/lib/cloner.py", line 159, in prepareRepo
17:59:27 repo.checkout(fetch_head)
17:59:27 File "/usr/local/lib/python2.7/dist-packages/zuul/merger/merger.py", line 127, in checkout
17:59:27 repo.head.reference = ref
17:59:27 File "/usr/lib/python2.7/dist-packages/git/refs/symbolic.py", line 301, in set_reference
17:59:27 fd = lfd.open(write=True, stream=True)
17:59:27 File "/usr/lib/python2.7/dist-packages/gitdb/util.py", line 314, in open
17:59:27 raise IOError("Lock at %r could not be obtained" % self._lockfilepath())
17:59:27 IOError: Lock at '/mnt/jenkins-workspace/workspace/mediawiki-phpunit-hhvm/src/.git/HEAD.lock' could not be obtained
17:59:27 Build step 'Execute shell' marked build as failure
17:59:27 [xUnit] [INFO] - Starting to record.
17:59:27 [xUnit] [INFO] - Processing PHPUnit-3.x (default)
17:59:27 [xUnit] [INFO] - [PHPUnit-3.x (default)] - 1 test report file(s) were found with the pattern 'log/junit-mw-phpunit.xml' relative to '/mnt/jenkins-workspace/workspace/mediawiki-phpunit-hhvm' for the testing framework 'PHPUnit-3.x (default)'.
17:59:27 [xUnit] [ERROR] - Test reports were found but not all of them are new. Did all the tests run?
17:59:27 * /mnt/jenkins-workspace/workspace/mediawiki-phpunit-hhvm/log/junit-mw-phpunit.xml is 3 days 18 hr old
17:59:27
17:59:27 [xUnit] [INFO] - Failing BUILD.
17:59:27 [xUnit] [INFO] - There are errors when processing test results.
17:59:27 [xUnit] [INFO] - Skipping tests recording.
17:59:27 [xUnit] [INFO] - Stop build.

https://integration.wikimedia.org/ci/job/mediawiki-phpunit-hhvm/1657/console
https://integration.wikimedia.org/ci/job/mediawiki-phpunit-hhvm/1570/console
https://integration.wikimedia.org/ci/job/mediawiki-phpunit-hhvm/1638/console
https://integration.wikimedia.org/ci/job/mediawiki-phpunit-hhvm/1636/console

Please investigate. Thanks.