Tests failing on Python 3.6

[theY4Kman]

On Python 3.6, all the tests appear to be erroring out with a traceback similar to this:

____________________ ERROR at setup of test_pytest_fixtures ____________________
.tox/py36/lib/python3.6/site-packages/django/db/migrations/state.py:409: in from_model
    fields.append((name, field.clone()))
.tox/py36/lib/python3.6/site-packages/django/db/models/fields/__init__.py:513: in clone
    name, path, args, kwargs = self.deconstruct()
.tox/py36/lib/python3.6/site-packages/django/db/models/fields/__init__.py:2378: in deconstruct
    name, path, args, kwargs = super().deconstruct()
.tox/py36/lib/python3.6/site-packages/django/db/models/fields/__init__.py:485: in deconstruct
    value = list(value)
E   TypeError: 'NoneType' object is not iterable
During handling of the above exception, another exception occurred:
.tox/py36/lib/python3.6/site-packages/pytest_djangoapp/plugin.py:20: in pytest_runtest_setup
    item.old_config = setup_databases()
.tox/py36/lib/python3.6/site-packages/django/test/runner.py:616: in setup_databases
    self.parallel, **kwargs
.tox/py36/lib/python3.6/site-packages/django/test/utils.py:174: in setup_databases
    serialize=connection.settings_dict['TEST'].get('SERIALIZE', True),
.tox/py36/lib/python3.6/site-packages/django/db/backends/base/creation.py:77: in create_test_db
    run_syncdb=True,
.tox/py36/lib/python3.6/site-packages/django/core/management/__init__.py:168: in call_command
    return command.execute(*args, **defaults)
.tox/py36/lib/python3.6/site-packages/django/core/management/base.py:371: in execute
    output = self.handle(*args, **options)
.tox/py36/lib/python3.6/site-packages/django/core/management/base.py:85: in wrapped
    res = handle_func(*args, **kwargs)
.tox/py36/lib/python3.6/site-packages/django/core/management/commands/migrate.py:202: in handle
    pre_migrate_apps = pre_migrate_state.apps
.tox/py36/lib/python3.6/site-packages/django/utils/functional.py:48: in __get__
    res = instance.__dict__[self.name] = self.func(instance)
.tox/py36/lib/python3.6/site-packages/django/db/migrations/state.py:208: in apps
    return StateApps(self.real_apps, self.models)
.tox/py36/lib/python3.6/site-packages/django/db/migrations/state.py:259: in __init__
    self.real_models.append(ModelState.from_model(model, exclude_rels=True))
.tox/py36/lib/python3.6/site-packages/django/db/migrations/state.py:414: in from_model
    e,
E   TypeError: Couldn't reconstruct field id on auth.Permission: 'NoneType' object is not iterable