py36 run-test: commands[3] | pytest
Traceback (most recent call last):
  File "/home/travis/build/microsoft/knack/.tox/py36/bin/pytest", line 7, in <module>
    from pytest import main
  File "/home/travis/build/microsoft/knack/.tox/py36/lib/python3.6/site-packages/pytest.py", line 13, in <module>
    from _pytest.fixtures import fixture, yield_fixture
  File "/home/travis/build/microsoft/knack/.tox/py36/lib/python3.6/site-packages/_pytest/fixtures.py", line 839, in <module>
    class FixtureFunctionMarker(object):
  File "/home/travis/build/microsoft/knack/.tox/py36/lib/python3.6/site-packages/_pytest/fixtures.py", line 841, in FixtureFunctionMarker
    params = attr.ib(convert=attr.converters.optional(tuple))
TypeError: attrib() got an unexpected keyword argument 'convert'
ERROR: InvocationError for command /home/travis/build/microsoft/knack/.tox/py36/bin/pytest (exited with code 1)
___________________________________ summary ____________________________________
ERROR:   py36: commands failed
The command "tox" exited with 1.