3.6.0: pytest is failing in one unit

I'm trying to package your module as an rpm package. So I'm using the typical build, install and test cycle used on building packages from non-root account.
"setup.py build"
"setup.py install --root </install/prefix>"
"pytest with PYTHONPATH pointing to sitearch and sitelib inside </install/prefix>
May I ask for help because few units are failing:
+ PYTHONPATH=/home/tkloczko/rpmbuild/BUILDROOT/python-ZConfig-3.6.0-2.fc35.x86_64/usr/lib64/python3.8/site-packages:/home/tkloczko/rpmbuild/BUILDROOT/python-ZConfig-3.6.0-2.fc35.x86_64/usr/lib/python3.8/site-packages
+ /usr/bin/pytest -ra
=========================================================================== test session starts ============================================================================
platform linux -- Python 3.8.12, pytest-6.2.5, py-1.10.0, pluggy-0.13.1
benchmark: 3.4.1 (defaults: timer=time.perf_counter disable_gc=False min_rounds=5 min_time=0.000005 max_time=1.0 calibration_precision=10 warmup=False warmup_iterations=100000)
Using --randomly-seed=2429164203
rootdir: /home/tkloczko/rpmbuild/BUILD/ZConfig-3.6.0
plugins: forked-1.3.0, shutil-1.7.0, virtualenv-1.7.0, expect-1.1.0, flake8-1.0.7, timeout-1.4.2, betamax-0.8.1, freezegun-0.4.2, aspectlib-1.5.2, toolbox-0.5, rerunfailures-9.1.1, requests-mock-1.9.3, cov-2.12.1, flaky-3.7.0, benchmark-3.4.1, xdist-2.3.0, pylama-7.7.1, datadir-1.3.1, regressions-2.2.0, cases-3.6.3, xprocess-0.18.1, black-0.3.12, anyio-3.3.0, asyncio-0.15.1, subtests-0.5.0, isort-2.0.0, hypothesis-6.14.6, mock-3.6.1, profiling-1.7.0, randomly-3.8.0, Faker-8.12.1, nose2pytest-1.0.8, pyfakefs-4.5.1, tornado-0.8.1, twisted-1.13.3, aiohttp-0.3.0
collected 360 items

ZConfig/tests/test_schema2html.py .............                                                                                                                      [  3%]
ZConfig/tests/test_cookbook.py ..                                                                                                                                    [  4%]
ZConfig/tests/test_cmdline.py ..........                                                                                                                             [  6%]
ZConfig/tests/test_matcher.py .......                                                                                                                                [  8%]
ZConfig/tests/test_cfgimports.py ......                                                                                                                              [ 10%]
ZConfig/tests/test_info.py ...............                                                                                                                           [ 14%]
ZConfig/components/logger/tests/test_logger.py ...............................................                                                                       [ 27%]
ZConfig/tests/test_schemaless.py ..                                                                                                                                  [ 28%]
ZConfig/tests/test_config.py ................                                                                                                                        [ 32%]
ZConfig/tests/test_validator.py ....F.                                                                                                                               [ 34%]
ZConfig/tests/test_loader.py .........................                                                                                                               [ 41%]
ZConfig/tests/test_schema.py ........................................................................................                                                [ 65%]
ZConfig/tests/test_readme.py .                                                                                                                                       [ 66%]
ZConfig/components/basic/tests/test_mapping.py ....                                                                                                                  [ 67%]
ZConfig/components/logger/tests/test_formatter.py ...........s...........................................sss................                                         [ 87%]
ZConfig/tests/test_subst.py .......                                                                                                                                  [ 89%]
ZConfig/tests/test_pygments.py .............                                                                                                                         [ 93%]
ZConfig/tests/test_datatypes.py ........................                                                                                                             [100%]

================================================================================= FAILURES =================================================================================
______________________________________________________________________ TestValidator.test_schema_only ______________________________________________________________________

self = <ZConfig.tests.test_validator.TestValidator testMethod=test_schema_only>

    def test_schema_only(self):
>       res = run_validator("--schema", support.input_file('simple.xml'))

ZConfig/tests/test_validator.py:42:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
ZConfig/tests/test_validator.py:24: in run_validator
    return validator.main(args)
ZConfig/validator.py:66: in main
    ZConfig.loadConfigFile(schema, f)
ZConfig/loader.py:115: in loadConfigFile
    return _get_config_loader(schema, overrides).loadFile(file, url)
ZConfig/loader.py:173: in loadFile
    return self.loadResource(r)
ZConfig/loader.py:411: in loadResource
    self._parse_resource(sm, resource)
ZConfig/loader.py:456: in _parse_resource
    parser.parse(matcher)
ZConfig/cfgparser.py:60: in parse
    done, line = self.nextline()
ZConfig/cfgparser.py:53: in nextline
    line = self.file.readline()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <_pytest.capture.DontReadFromInput object at 0x7f4ced7decd0>, args = ()

    def read(self, *args):
>       raise OSError(
            "pytest: reading from stdin while output is captured!  Consider using `-s`."
        )
E       OSError: pytest: reading from stdin while output is captured!  Consider using `-s`.

/usr/lib/python3.8/site-packages/_pytest/capture.py:217: OSError
========================================================================= short test summary info ==========================================================================
SKIPPED [1] ZConfig/components/logger/tests/test_formatter.py:361: Only applies for Python 2.
SKIPPED [1] ZConfig/components/logger/tests/test_formatter.py:412: Only applies for Python 2.
SKIPPED [1] ZConfig/components/logger/tests/test_formatter.py:379: Only applies for Python 2.
SKIPPED [1] ZConfig/components/logger/tests/test_formatter.py:436: Only applies for Python 2.
FAILED ZConfig/tests/test_validator.py::TestValidator::test_schema_only - OSError: pytest: reading from stdin while output is captured!  Consider using `-s`.
================================================================= 1 failed, 355 passed, 4 skipped in 2.51s =================================================================
pytest-xprocess reminder::Be sure to terminate the started process by running 'pytest --xkill' if you have not explicitly done so in your fixture with 'xprocess.getinfo(<process_name>).terminate()'.
zopefoundation / ZConfig

3.6.0: pytest is failing in one unit #83
