pytest issues warning about unicode warnings containign non-ascii even if it only contains ascii chars

[fabioz]

pytest: 3.2.1
python: 2.7.12
Windows 10

The test below reproduces the error (the first warning with bytes will work as expected and the second will break pytest).

def test_warnings():
    import warnings
    warnings.warn(b'Something')
    warnings.warn(u'Something')

Error:

============================= test session starts =============================
platform win32 -- Python 2.7.12, pytest-3.2.1, py-1.4.34, pluggy-0.4.0
session-tmp-dir: W:\scbr\Projects\scbr\tmp\tmp-23
rootdir: W:\scbr\Projects\scbr, inifile: pytest.ini
plugins: catchlog-1.2.2, cov-2.5.1, cpp-0.4.4, forked-0.2, localserver-0.3.6, mock-1.6.2, timeout-1.2.0, xdist-1.20.0
collected 1 item

snippet.py .
INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\main.py", line 110, in wrap_session
INTERNALERROR>     session.exitstatus = doit(config, session) or 0
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\main.py", line 146, in _main
INTERNALERROR>     config.hook.pytest_runtestloop(session=session)
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 745, in __call__
INTERNALERROR>     return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 339, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 334, in <lambda>
INTERNALERROR>     _MultiCall(methods, kwargs, hook.spec_opts).execute()
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 614, in execute
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\main.py", line 169, in pytest_runtestloop
INTERNALERROR>     item.config.hook.pytest_runtest_protocol(item=item, nextitem=nextitem)
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 745, in __call__
INTERNALERROR>     return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 339, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 334, in <lambda>
INTERNALERROR>     _MultiCall(methods, kwargs, hook.spec_opts).execute()
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 613, in execute
INTERNALERROR>     return _wrapped_call(hook_impl.function(*args), self.execute)
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 254, in _wrapped_call
INTERNALERROR>     return call_outcome.get_result()
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 280, in get_result
INTERNALERROR>     _reraise(*ex)  # noqa
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 265, in __init__
INTERNALERROR>     self.result = func()
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 613, in execute
INTERNALERROR>     return _wrapped_call(hook_impl.function(*args), self.execute)
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\vendored_packages\pluggy.py", line 250, in _wrapped_call
INTERNALERROR>     wrap_controller.send(call_outcome)
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\warnings.py", line 94, in pytest_runtest_protocol
INTERNALERROR>     yield
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\contextlib.py", line 24, in __exit__
INTERNALERROR>     self.gen.next()
INTERNALERROR>   File "W:\scbr\envs\scbr-py27\lib\site-packages\_pytest\warnings.py", line 88, in catch_warnings_for_item
INTERNALERROR>     UnicodeWarning)
INTERNALERROR> UnicodeWarning: Warning is using unicode non convertible to ascii, converting to a safe representation:
INTERNALERROR>   W:\scbr\Projects\scbr\source\python\snippet.py:5: UserWarning: Something
INTERNALERROR>   warnings.warn(u'Something')

[fabioz]

Note: just did some more tests and apparently this error happens only when the PYTHONWARNINGS env variable is set to error::UnicodeWarning::

i.e.:
set PYTHONWARNINGS=error::UnicodeWarning::

Still, note that the unicode passed is convertible to ascii (so, pytest itself should not give a new warning which causes the exception to be raised and gives the internal error).

[nicoddemus]

Thanks @fabioz!

[bilderbuchi]

@nicoddemus @RonnyPfannschmidt as the #2810 is merged this can be closed I think.

[nicoddemus]

Yes thank you!