i've seen on clean installs (no venv yet) that cbuildbot_run flakes heavily until venv has been fully initialized

the bots are showing this too sometimes:
https://uberchromegw.corp.google.com/i/chromeos/builders/poppy-release/builds/657/steps/UnitTest/logs/stdio

chromite-0.0.2-r3272: 20:23:57: INFO: Finished [198/198] lib/workqueue/tasks_unittest (0:01:19.262856)
chromite-0.0.2-r3272: 
chromite-0.0.2-r3272: 20:23:57: ERROR: ### LOG: scripts/extract_gerrit_history_unittest
chromite-0.0.2-r3272: Traceback (most recent call last):
chromite-0.0.2-r3272:   File "/usr/lib64/python2.7/runpy.py", line 162, in _run_module_as_main
chromite-0.0.2-r3272:     "__main__", fname, loader, pkg_name)
chromite-0.0.2-r3272:   File "/usr/lib64/python2.7/runpy.py", line 72, in _run_code
chromite-0.0.2-r3272:     exec code in run_globals
chromite-0.0.2-r3272:   File "/mnt/host/source/infra_virtualenv/venv/cros_venv/scripts/create_venv.py", line 46, in <module>
chromite-0.0.2-r3272:     main()
chromite-0.0.2-r3272:   File "/mnt/host/source/infra_virtualenv/venv/cros_venv/scripts/create_venv.py", line 35, in main
chromite-0.0.2-r3272:     print(venv.ensure())
chromite-0.0.2-r3272:   File "/mnt/host/source/infra_virtualenv/venv/cros_venv/venvlib.py", line 173, in ensure
chromite-0.0.2-r3272:     with flock.FileLock(self._paths.lockfile):
chromite-0.0.2-r3272:   File "/mnt/host/source/infra_virtualenv/venv/cros_venv/flock.py", line 69, in __enter__
chromite-0.0.2-r3272:     self._acquire_lock()
chromite-0.0.2-r3272:   File "/mnt/host/source/infra_virtualenv/venv/cros_venv/flock.py", line 78, in _acquire_lock
chromite-0.0.2-r3272:     self._clean_stale_lock()
chromite-0.0.2-r3272:   File "/mnt/host/source/infra_virtualenv/venv/cros_venv/flock.py", line 107, in _clean_stale_lock
chromite-0.0.2-r3272:     self._clean_orphaned_lock()
chromite-0.0.2-r3272:   File "/mnt/host/source/infra_virtualenv/venv/cros_venv/flock.py", line 117, in _clean_orphaned_lock
chromite-0.0.2-r3272:     if self._is_lock_orphaned():
chromite-0.0.2-r3272:   File "/mnt/host/source/infra_virtualenv/venv/cros_venv/flock.py", line 129, in _is_lock_orphaned
chromite-0.0.2-r3272:     and not _is_pid_running(self._get_lock_pid()))
chromite-0.0.2-r3272:   File "/mnt/host/source/infra_virtualenv/venv/cros_venv/flock.py", line 133, in _get_lock_pid
chromite-0.0.2-r3272:     return _procdir.getpid(os.readlink(self._lockfile))
chromite-0.0.2-r3272: OSError: [Errno 2] No such file or directory: '/home/chrome-bot/.cache/cros_venv/venv-2.7.10-e5e7c29bac8f6c49d86dffd36c05d6fa/change.lock'
chromite-0.0.2-r3272: Traceback (most recent call last):
chromite-0.0.2-r3272:   File "scripts/extract_gerrit_history_unittest", line 93, in <module>
chromite-0.0.2-r3272:     main()
chromite-0.0.2-r3272:   File "scripts/extract_gerrit_history_unittest", line 31, in main
chromite-0.0.2-r3272:     venvdir = _CreateVenv()
chromite-0.0.2-r3272:   File "scripts/extract_gerrit_history_unittest", line 39, in _CreateVenv
chromite-0.0.2-r3272:     _REQUIREMENTS,
chromite-0.0.2-r3272:   File "/usr/lib64/python2.7/subprocess.py", line 573, in check_output
chromite-0.0.2-r3272:     raise CalledProcessError(retcode, cmd, output=output)
chromite-0.0.2-r3272: subprocess.CalledProcessError: Command '['/mnt/host/source/chromite/../infra_virtualenv/bin/create_venv', '/mnt/host/source/chromite/venv/requirements.txt']' returned non-zero exit status 1