so the fixture teardown method was attempting to delete all the fixture data. only some of my tests had...already deleted the fixture data. and the teardown method gets unhappy when what it deletes doesn't match what it created.

for now this is all being applied to an in-memory sqlite db (yes, i know that leaves holes in my tests), so i'm just going to skip it for now. when i move off sqlite, i'll rewrite the offending tests so the fixtures can clean up after themselves.