Attempting to migrate a project from Django 1.7 to 1.8. After wrestling with code errors, I'm able to get migrations to run. However, when I try to migrate, I'm given the error "'NoneType' object has no attribute '_meta'"

There's no reference in the traceback to any of my apps, so I'm unsure of where exactly to go about looking for the bug (as well as which code to include here so I can be more helpful to those trying to help me)

Here's the full text of the traceback

(venv)rtownley@ubuntu:~/Projects/sparrow1/NJ$ ./manage.py makemigrations
No changes detected
(venv)rtownley@ubuntu:~/Projects/sparrow1/NJ$ ./manage.py migrate
Operations to perform:Synchronize unmigrated apps: staticfiles, editor, djcelery, messages, getty, kombu_transport_django, debug_toolbar, utils, locking, petro, tokenapi, grappelli, django_extensions, selectableApply all migrations: adops, taxonomy, issues, editorial, contenttypes, authors, auth, comms, membership, sessions, bento, urlalias, accounts, breaking_news, easy_thumbnails, images, admin, pages, documents, events
Synchronizing apps without migrations:Creating tables...Running deferred SQL...Installing custom SQL...
Running migrations:Rendering model states...Traceback (most recent call last):File "./manage.py", line 10, in <module>execute_from_command_line(sys.argv)File "/home/rtownley/Projects/sparrow1/venv/lib/python3.4/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_lineutility.execute()File "/home/rtownley/Projects/sparrow1/venv/lib/python3.4/site-packages/django/core/management/__init__.py", line 330, in executeself.fetch_command(subcommand).run_from_argv(self.argv)File "/home/rtownley/Projects/sparrow1/venv/lib/python3.4/site-packages/django/core/management/base.py", line 390, in run_from_argvself.execute(*args, **cmd_options)File "/home/rtownley/Projects/sparrow1/venv/lib/python3.4/site-packages/django/core/management/base.py", line 441, in executeoutput = self.handle(*args, **options)File "/home/rtownley/Projects/sparrow1/venv/lib/python3.4/site-packages/django/core/management/commands/migrate.py", line 221, in handleexecutor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)File "/home/rtownley/Projects/sparrow1/venv/lib/python3.4/site-packages/django/db/migrations/executor.py", line 104, in migratestate = migration.mutate_state(state, preserve=do_run)File "/home/rtownley/Projects/sparrow1/venv/lib/python3.4/site-packages/django/db/migrations/migration.py", line 83, in mutate_stateoperation.state_forwards(self.app_label, new_state)File "/home/rtownley/Projects/sparrow1/venv/lib/python3.4/site-packages/django/db/migrations/operations/fields.py", line 51, in state_forwardsstate.reload_model(app_label, self.model_name_lower)File "/home/rtownley/Projects/sparrow1/venv/lib/python3.4/site-packages/django/db/migrations/state.py", line 97, in reload_modelrelated_models = get_related_models_recursive(old_model)File "/home/rtownley/Projects/sparrow1/venv/lib/python3.4/site-packages/django/db/migrations/state.py", line 57, in get_related_models_recursiverel_app_label, rel_model_name = rel_mod._meta.app_label, rel_mod._meta.model_name
AttributeError: 'NoneType' object has no attribute '_meta'

Other pieces that could potentially be at play: -I have a custom handler that listens for the save event, serializes the data, and creates an identical object in Mongo -Operating out of a virtual environment running Python3.4

Any thoughts on where to go about hunting for the error? Thanks, and sorry I can't provide more code yet!

Thanks to meiamsome, I figured it out: one of my models had a ForeignKey relationship to a model that no longer existed (I had removed it, and a Git merge had added it back). Thanks for the help all!