Issue upgrading to Wagtail 2.1 - django

Question

Upgraded from Wagtail 2.0 to 2.1. Running on an Ubuntu vagrant box.
I get the error below when running any manage.py command after upgrading from Wagtail 2.0 to 2.1 or 2.11. If I downgrade back to 2.0 it works again, so I'm sure I have some incorrect dependencies in there...
Any thoughts on how to resolve this?
Traceback (most recent call last):
File "./manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/django/core/management/__init__.py", line 371, in execute_from_command_line
utility.execute()
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/django/core/management/__init__.py", line 347, in execute
django.setup()
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/django/__init__.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/django/apps/registry.py", line 89, in populate
app_config = AppConfig.create(entry)
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/django/apps/config.py", line 116, in create
mod = import_module(mod_path)
File "/usr/local/Cellar/python3/3.6.3/Frameworks/Python.framework/Versions/3.6/lib/python3.6/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 994, in _gcd_import
File "<frozen importlib._bootstrap>", line 971, in _find_and_load
File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 678, in exec_module
File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/wagtail/search/apps.py", line 4, in <module>
from wagtail.search.signal_handlers import register_signal_handlers
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/wagtail/search/signal_handlers.py", line 3, in <module>
from wagtail.search import index
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/wagtail/search/index.py", line 10, in <module>
from modelcluster.fields import ParentalManyToManyField
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/modelcluster/fields.py", line 19, in <module>
from modelcluster.models import get_related_model, ClusterableModel
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/modelcluster/models.py", line 152, in <module>
class ClusterableModel(models.Model):
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/django/db/models/base.py", line 100, in __new__
app_config = apps.get_containing_app_config(module)
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/django/apps/registry.py", line 244, in get_containing_app_config
self.check_apps_ready()
File "/Users/chrisrogers/blog/lib/python3.6/site-packages/django/apps/registry.py", line 127, in check_apps_ready
raise AppRegistryNotReady("Apps aren't loaded yet.")
django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.
My req.txt is below:
Django==2.0
Jinja2==2.8
Markdown==2.6.2
MarkupSafe==0.23
Pillow>2.8.2
PyYAML==3.11
Pygments==2.0.2
Unidecode==0.04.18
Willow>0.2.2
ansible==2.0.1.0
beautifulsoup4==4.4.0
django-appconf==1.0.1
django-compressor==1.5
django-medusa==0.3.0
django-modelcluster==1.1
django-sendfile==0.3.10
django-taggit==0.18.0
django-treebeard==3.0
djangorestframework==3.7
ecdsa==0.13
elasticsearch==1.7.0
google-api-python-client==1.5.0
html5lib==0.999
httplib2==0.9.2
oauth2client==2
paramiko==1.16.0
postgres==2.1.2
psycopg2-binary==2.7.4
wagalytics==0.7
wagtail==2.1
wagtailfontawesome==1.1.3
wheel==0.24.0

Answer 1

You should upgrade django-modelcluster.
pip install django-modelcluster==4.1