Tests that need to be re-worked

[tacaswell]

While going through databroker tests with @danielballan doing the final prep for v2 there are a number of tests that need to be re-worked or moved else where

• [ ] testing the behavior of multiple runs being found from a partial uid in test_broker.py:test_partial_uid_lookup. The issue with the current implementation makes 50 runs and then searches on a single letter (which means we are sure to have at least one duplicate), however because tiled does not support partial uid access with less than 5 characters this fails for other reasons. Rather than generating enough runs to be sure we randomly get a collision 😱 , we need to use event model's document machinery to intentionally generate colliding runs and insert them into the database. This test was originally written before we had RE-independent ways to generate the documents we can also drop most of the fixtures!
• [ ] move the tests that things fail as expected when handlers are missing to the server side, see test_broker.py:test_external_access_with_handler