update pytest config (#4463)

* update pytest config

pytest 3.8.0 was just released and officially deprecates some of the way
we do pytest marks. They introduced a new way to do this in 3.6 so this
PR switches to that mechanism and updates our minimum pytest requirement

* update the stubs

* also update wycheproof test config to remove deprecated paths

* don't need this any more
4 files changed