py-test: updated to 3.5.1

Pytest 3.5.1:
Bug Fixes
Reset sys.last_type, sys.last_value and sys.last_traceback before each test executes. Those attributes are added by pytest during the test run to aid debugging, but were never reset so they would create a leaking reference to the last failing test窶冱 frame which in turn could never be reclaimed by the garbage collector.
pytest.raises now raises TypeError when receiving an unknown keyword argument.
pytest.raises now works with exception classes that look like iterables.

Improved Documentation
Fix typo in caplog fixture documentation, which incorrectly identified certain attributes as methods.

Trivial/Internal Changes
Added a more indicative error message when parametrizing a function whose argument takes a default value.
Remove internal _pytest.terminal.flatten function in favor of more_itertools.collapse.
Import some modules from collections.abc instead of collections as the former modules trigger DeprecationWarning in Python 3.7.
record_property is no longer experimental, removing the warnings was forgotten.
Mention in documentation and CLI help that fixtures with leading _ are printed by pytest --fixtures only if the -v option is added.


(adam)