RuntimeError when maximum workers are reached

[nicoddemus]

import os
import pytest

@pytest.mark.parametrize('i', range(10))
def test_crash(i):
    os._exit(1)

λ pytest .tmp\test_crash.py  -n2 --max-worker-restart=4
===================================================================================== test session starts ====================================================================================== platform win32 -- Python 3.7.3, pytest-4.6.2, py-1.8.0, pluggy-0.12.0
rootdir: C:\Users\bruno.ESSS.CO\pytest-xdist, inifile: tox.ini
plugins: forked-1.0.2, xdist-1.28.1.dev1+g9fcf8fa
gw0 [10] / gw1 [10]
[gw1] node down: Not properly terminated
fReplacing crashed worker gw1
gw0 [10] / gw2 C   [gw0] node down: Not properly terminated
fReplacing crashed worker gw0
gw3 C / gw2 [10][gw2] node down: Not properly terminated
fReplacing crashed worker gw2
gw3 [10] / gw4 C[gw3] node down: Not properly terminated
fReplacing crashed worker gw3
gw5 C / gw4 [10][gw4] node down: Not properly terminated
fMaximum crashed workers reached: 4
gw5 [10] / gw4 [10][gw5] node down: Not properly terminated
fMaximum crashed workers reached: 4
INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "c:\users\bruno.esss.co\pytest-xdist\.env37\lib\site-packages\_pytest\main.py", line 206, in wrap_session
INTERNALERROR>     session.exitstatus = doit(config, session) or 0
INTERNALERROR>   File "c:\users\bruno.esss.co\pytest-xdist\.env37\lib\site-packages\_pytest\main.py", line 250, in _main
INTERNALERROR>     config.hook.pytest_runtestloop(session=session)
INTERNALERROR>   File "c:\users\bruno.esss.co\pytest-xdist\.env37\lib\site-packages\pluggy\hooks.py", line 289, in __call__
INTERNALERROR>     return self._hookexec(self, self.get_hookimpls(), kwargs)
INTERNALERROR>   File "c:\users\bruno.esss.co\pytest-xdist\.env37\lib\site-packages\pluggy\manager.py", line 87, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "c:\users\bruno.esss.co\pytest-xdist\.env37\lib\site-packages\pluggy\manager.py", line 81, in <lambda>
INTERNALERROR>     firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
INTERNALERROR>   File "c:\users\bruno.esss.co\pytest-xdist\.env37\lib\site-packages\pluggy\callers.py", line 208, in _multicall
INTERNALERROR>     return outcome.get_result()
INTERNALERROR>   File "c:\users\bruno.esss.co\pytest-xdist\.env37\lib\site-packages\pluggy\callers.py", line 80, in get_result
INTERNALERROR>     raise ex[1].with_traceback(ex[2])
INTERNALERROR>   File "c:\users\bruno.esss.co\pytest-xdist\.env37\lib\site-packages\pluggy\callers.py", line 187, in _multicall
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "c:\users\bruno.esss.co\pytest-xdist\xdist\dsession.py", line 118, in pytest_runtestloop
INTERNALERROR>     self.loop_once()
INTERNALERROR>   File "c:\users\bruno.esss.co\pytest-xdist\xdist\dsession.py", line 130, in loop_once
INTERNALERROR>     raise RuntimeError("Unexpectedly no active workers available")
INTERNALERROR> RuntimeError: Unexpectedly no active workers available