This buildbot is failing when raising when creating subprocess.CalledProcessError:

https://buildbot.python.org/all/#/builders/40/builds/1135/steps/3/logs/stdio

test_defaults (test.test_venv.BasicTest) ... ok
test_executable (test.test_venv.BasicTest) ... ok
test_executable_symlinks (test.test_venv.BasicTest) ... skipped 'Needs symlinks'
test_isolation (test.test_venv.BasicTest) ... ok
test_overwrite_existing (test.test_venv.BasicTest) ... ok
test_prefixes (test.test_venv.BasicTest) ... ok
test_prompt (test.test_venv.BasicTest) ... ok
test_symlinking (test.test_venv.BasicTest) ... skipped 'Needs symlinks'
test_unicode_in_batch_file (test.test_venv.BasicTest) ... ERROR
test_unoverwritable_fails (test.test_venv.BasicTest) ... ok
test_upgrade (test.test_venv.BasicTest) ... ok
test_devnull (test.test_venv.EnsurePipTest) ... ok
test_explicit_no_pip (test.test_venv.EnsurePipTest) ... ok
test_no_pip_by_default (test.test_venv.EnsurePipTest) ... ok
test_with_pip (test.test_venv.EnsurePipTest) ... ok
======================================================================
ERROR: test_unicode_in_batch_file (test.test_venv.BasicTest)
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Traceback (most recent call last):
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\test\test_venv.py", line 302, in test_unicode_in_batch_file
    out, err = check_output(
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\test\test_venv.py", line 37, in check_output
    raise subprocess.CalledProcessError(
TypeError: __init__() takes from 3 to 5 positional arguments but 6 were given
----------------------------------------------------------------------
I will prepare a PR fixing this