Turn warnings into errors in the test suite

[nicoddemus]

Currently the test suite is issuing this warnings:

=============================== warnings summary ===============================
testing/test_method_ordering.py::test_add_tracefuncs[spec-is-class]
  /home/travis/build/nicoddemus/pluggy/.tox/py34/lib/python3.4/site-packages/pluggy/__init__.py:678: UserWarning: Argument(s) ('arg',) which are declared in the hookspec can not be found in this hook call
    .format(tuple(notincall))
testing/test_method_ordering.py::test_add_tracefuncs[spec-is-instance]
  /home/travis/build/nicoddemus/pluggy/.tox/py34/lib/python3.4/site-packages/pluggy/__init__.py:678: UserWarning: Argument(s) ('arg',) which are declared in the hookspec can not be found in this hook call
    .format(tuple(notincall))
testing/test_pluginmanager.py::test_call_with_too_few_args
  /home/travis/build/nicoddemus/pluggy/.tox/py34/lib/python3.4/site-packages/pluggy/__init__.py:678: UserWarning: Argument(s) ('arg',) which are declared in the hookspec can not be found in this hook call
    .format(tuple(notincall))
-- Docs: http://doc.pytest.org/en/latest/warnings.html

Turning them into errors or at least mark them as "known" is a good way to catch incompatibilities early.

[goodboy]

@nicoddemus yeah test_call_with_too_few_args is obviously an intentional case but the first two can probably just be fixed.

We can error on warnings with pytest setting yah?

[nicoddemus]

Yep, just configure it on pytest.ini:

[pytest]
filterwarnings =
    error

[goodboy]

Hit the first problem:

DeprecationWarning: inspect.getargspec() is deprecated, use inspect.signature() or inspect.getfullargspec()

For py2 we need inspect.getargspec() but on py3 we're supposed to use inspect.signature (3.5+) or inspect.getfullargspec (3 < py < 3.5).

Doing a quick search the dual compatibility fix looks something this.

I think we'll need a separate issue for that.

[RonnyPfannschmidt]

i wonder if it would work to just go for funcsigs2 on python2 (its a backport)

[nicoddemus]

If that works I would rather that than cook something up.