Getting error with pytest OSError: [WinError 87] The parameter is incorrect

I have installed pytest but getting the following error while testing pytest --version in command prompt:

Traceback (most recent call last): File "C:\Python\Scripts\pytest-script.py", line 11, in <module> load_entry_point('pytest==5.1.0', 'console_scripts', 'pytest')() File "c:\python\lib\site-packages\pytest-5.1.0-py3.7.egg\_pytest\config\__init__.py", line 58, in main config = _prepareconfig(args, plugins) File "c:\python\lib\site-packages\pytest-5.1.0-py3.7.egg\_pytest\config\__init__.py", line 208, in _prepareconfig pluginmanager=pluginmanager, args=args File "c:\python\lib\site-packages\pluggy\hooks.py", line 289, in __call__ return self._hookexec(self, self.get_hookimpls(), kwargs) File "c:\python\lib\site-packages\pluggy\manager.py", line 87, in _hookexec return self._inner_hookexec(hook, methods, kwargs) File "c:\python\lib\site-packages\pluggy\manager.py", line 81, in <lambda> firstresult=hook.spec.opts.get("firstresult") if hook.spec else False, File "c:\python\lib\site-packages\pluggy\callers.py", line 203, in _multicall gen.send(outcome) File "c:\python\lib\site-packages\pytest-5.1.0-py3.7.egg\_pytest\helpconfig.py", line 89, in pytest_cmdline_parse config = outcome.get_result() File "c:\python\lib\site-packages\pluggy\callers.py", line 80, in get_result raise ex[1].with_traceback(ex[2]) File "c:\python\lib\site-packages\pluggy\callers.py", line 187, in _multicall res = hook_impl.function(*args) File "c:\python\lib\site-packages\pytest-5.1.0-py3.7.egg\_pytest\config\__init__.py", line 716, in pytest_cmdline_parse self.parse(args) File "c:\python\lib\site-packages\pytest-5.1.0-py3.7.egg\_pytest\config\__init__.py", line 924, in parse self._preparse(args, addopts=addopts) File "c:\python\lib\site-packages\pytest-5.1.0-py3.7.egg\_pytest\config\__init__.py", line 880, in _preparse early_config=self, args=args, parser=self._parser File "c:\python\lib\site-packages\pluggy\hooks.py", line 289, in __call__ return self._hookexec(self, self.get_hookimpls(), kwargs) File "c:\python\lib\site-packages\pluggy\manager.py", line 87, in _hookexec return self._inner_hookexec(hook, methods, kwargs) File "c:\python\lib\site-packages\pluggy\manager.py", line 81, in <lambda> firstresult=hook.spec.opts.get("firstresult") if hook.spec else False, File "c:\python\lib\site-packages\pluggy\callers.py", line 208, in _multicall return outcome.get_result() File "c:\python\lib\site-packages\pluggy\callers.py", line 80, in get_result raise ex[1].with_traceback(ex[2]) File "c:\python\lib\site-packages\pluggy\callers.py", line 182, in _multicall next(gen) # first yield File "c:\python\lib\site-packages\pytest-5.1.0-py3.7.egg\_pytest\capture.py", line 42, in pytest_load_initial_conftests _py36_windowsconsoleio_workaround(sys.stdout) File "c:\python\lib\site-packages\pytest-5.1.0-py3.7.egg\_pytest\capture.py", line 819, in _py36_windowsconsoleio_workaround sys.stdin = _reopen_stdio(sys.stdin, "rb") File "c:\python\lib\site-packages\pytest-5.1.0-py3.7.egg\_pytest\capture.py", line 812, in _reopen_stdio open(os.dup(f.fileno()), mode, buffering), OSError: [WinError 87] The parameter is incorrect 

How can I fix it?

1 Answer

Looks like this is due to a pytest/Python bug:

For now you could downgrade to Python 3.7.3 until someone finds a workaround.