Travis builds fail with PyTest 4

[smmaurer]

Travis builds are failing currently for the Pandana master branch: https://travis-ci.org/UDST/pandana

They passed 4 months ago when the last PR was merged, and were triggered again today because I added a version tag. It looks like they're failing now because of a change in the PyTest command line syntax, but i haven't dug into it yet.

[smmaurer]

I got the test builds working for the time being by specifying pytest<4.0 in the Travis script.

It's not clear to me what in PyTest 4 broke our syntax. The test invocations in setup.py are pretty complicated.

https://docs.pytest.org/en/latest/changelog.html

The last working build (430) installed PyTest 3.8, and the first failing build (431) installed PyTest 4.1.1.

https://travis-ci.org/UDST/pandana/builds/429668388 (430)
https://travis-ci.org/UDST/pandana/builds/485669326 (431)

This is hard for me to troubleshoot locally because of C compilation issues.