Pytest seems to be wrapping fixtures multiple times when they are declared in testing modules, and recent versions of pytest prevent fixture re-wrapping, and therefore all fixture declarations must be moved to separate (non-testing) modules, e.g. tests/fixtures.py.
Tests are failing on master: https://travis-ci.org/github/RhodiumGroup/rhg_compute_tools/jobs/672710341#L2716
This was originally discovered in @dpa9694's PR https://github.com/RhodiumGroup/rhg_compute_tools/pull/65.
Looks like this is related: https://github.com/pytest-dev/pytest/issues/3518
Pytest seems to be wrapping fixtures multiple times when they are declared in testing modules, and recent versions of pytest prevent fixture re-wrapping, and therefore all fixture declarations must be moved to separate (non-testing) modules, e.g.
tests/fixtures.py.