pytest >= 5.4.0 raises INTERNALERROR AttributeError with pytest-sugar installed

[DomKennedy]

With both 5.4.0 and 5.4.1, running pytest in the following environment:

``` $ pip list Package Version ------------------ ------- apipkg 1.5 attrs 19.3.0 coverage 5.0.4 execnet 1.7.1 importlib-metadata 1.5.0 more-itertools 8.2.0 packaging 20.3 pip 20.0.2 pluggy 0.13.1 py 1.8.1 pyparsing 2.4.6 pytest 5.4.1 pytest-cov 2.8.1 pytest-forked 1.1.3 pytest-html 2.1.1 pytest-metadata 1.8.0 pytest-sugar 0.9.2 pytest-xdist 1.31.0 setuptools 46.0.0 six 1.14.0 termcolor 1.1.0 wcwidth 0.1.8 wheel 0.34.2 zipp 3.1.0 ```

Raises the following error:

INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "~/foo/.venv/lib/python3.6/site-packages/_pytest/main.py", line 187, in wrap_session
INTERNALERROR>     config._do_configure()
:INTERNALERROR>   File "~/foo/.venv/lib/python3.6/site-packages/_pytest/config/__init__.py", line 820, in _do_configure
INTERNALERROR>     self.hook.pytest_configure.call_historic(kwargs=dict(config=self))
INTERNALERROR>   File "~/foo/.venv/lib/python3.6/site-packages/pluggy/hooks.py", line 308, in call_historic
INTERNALERROR>     res = self._hookexec(self, self.get_hookimpls(), kwargs)
INTERNALERROR>   File "~/foo/.venv/lib/python3.6/site-packages/pluggy/manager.py", line 93, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "~/foo/.venv/lib/python3.6/site-packages/pluggy/manager.py", line 87, in <lambda>
INTERNALERROR>     firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
INTERNALERROR>   File "/~foo/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 208, in _multicall
INTERNALERROR>     return outcome.get_result()
INTERNALERROR>   File "~/foo/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 80, in get_result
INTERNALERROR>     raise ex[1].with_traceback(ex[2])
INTERNALERROR>   File "~/foo/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 187, in _multicall
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "~/foo/.venv/lib/python3.6/site-packages/pytest_sugar.py", line 171, in pytest_configure
INTERNALERROR>     sugar_reporter = SugarTerminalReporter(standard_reporter)
INTERNALERROR>   File "~/foo/.venv/lib/python3.6/site-packages/pytest_sugar.py", line 209, in __init__
INTERNALERROR>    self.writer = self._tw
INTERNALERROR> AttributeError: can't set attribute

Note that the above environment is the result of installing the following requirements into a clean virtualenv:

pytest
pytest-cov
pytest-forked
pytest-html
pytest-metadata
pytest-sugar
pytest-xdist

Uninstalling pytest-sugar fixes the issue, as does downgrading pytest to 5.3.5.

I've experienced this error with python 3.6.8 on Ubuntu 18.04, and python 3.7.3 on macOS Catalina.

[The-Compiler]

Accessing writer never really was meant to be public, and thus was deprecated in 5.4, see #6784. However, that deprecation warning probably should be shown when trying to set it as well.

[DomKennedy]

Ah, indeed there is indeed already a bug report for this on pytest-sugar: Teemu/pytest-sugar#187

[The-Compiler]

Given that this is a regression, I still think there's something for pytest to fix here (adjusting the deprecated property so that setting the attribute still works), no? @nicoddemus what do you think?

[RonnyPfannschmidt]

there should be a setter that sets self._tw and warns