pytest<4.3 + latest attrs => TypeError: attrib() got an unexpected keyword argument 'convert'

[asottile]

Seems attrs 19.2 contains a breaking change:

$ pytest --help
Traceback (most recent call last):
  File "/tmp/x/venv/bin/pytest", line 6, in <module>
    from pytest import main
  File "/tmp/x/venv/lib/python3.6/site-packages/pytest.py", line 13, in <module>
    from _pytest.fixtures import fixture, yield_fixture
  File "/tmp/x/venv/lib/python3.6/site-packages/_pytest/fixtures.py", line 832, in <module>
    class FixtureFunctionMarker(object):
  File "/tmp/x/venv/lib/python3.6/site-packages/_pytest/fixtures.py", line 834, in FixtureFunctionMarker
    params = attr.ib(convert=attr.converters.optional(tuple))
TypeError: attrib() got an unexpected keyword argument 'convert'

The fix is to either upgrade pytest or to downgrade attrs

[asottile]

just creating this so there's visibility -- CC @hynek in case anyone hits this from the attrs side ;)

[jaraco]

To be clear, downgrade means attrs<19.2.