Pulp

See this PR as an example:

https://github.com/pulp/pulp/pull/3591

Here's the failing test:

======================================================================
ERROR: test_state_validation (unit.server.db.model.test_dispatch.TestTaskStatus)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/jenkins/workspace/unittest-pulp-pr/node-type/f27-os/pulp/server/test/unit/server/db/model/test_dispatch.py", line 169, in test_state_validation
    state=invalid_state).save)
  File "/usr/lib64/python2.7/unittest/case.py", line 511, in assertRaises
    callableObj(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/mongoengine/document.py", line 362, in save
    self.validate(clean=clean)
  File "/usr/lib/python2.7/site-packages/mongoengine/base/document.py", line 379, in validate
    field._validate(value)
  File "/usr/lib/python2.7/site-packages/mongoengine/base/fields.py", line 224, in _validate
    self._validate_choices(value)
  File "/usr/lib/python2.7/site-packages/mongoengine/base/fields.py", line 218, in _validate_choices
    if len(set(values) - set(choice_list)):
TypeError: unhashable type: 'dict'

It looks like the tests started failing sometime between August 14-17. I think there was an upgrade from mongoengine 0.15.1 to 0.15.3.