Including new app causing AttributeError: 'str' object has no attribute '_meta' in Python/Django app -

using python 2.7 , django 1.9.9 i'm getting following error when try in include app developing within installed_aps

traceback (most recent call last):   file "manage.py", line 22, in <module>     execute_from_command_line(sys.argv)   file "/var/www/cltc/env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 353, in execute_from_command_line     utility.execute()   file "/var/www/cltc/env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 345, in execute     self.fetch_command(subcommand).run_from_argv(self.argv)   file "/var/www/cltc/env/local/lib/python2.7/site-packages/django/core/management/base.py", line 348, in run_from_argv     self.execute(*args, **cmd_options)   file "/var/www/cltc/env/local/lib/python2.7/site-packages/django/core/management/base.py", line 398, in execute     self.check()   file "/var/www/cltc/env/local/lib/python2.7/site-packages/django/core/management/base.py", line 426, in check     include_deployment_checks=include_deployment_checks,   file "/var/www/cltc/env/local/lib/python2.7/site-packages/django/core/checks/registry.py", line 75, in run_checks     new_errors = check(app_configs=app_configs)   file "/var/www/cltc/env/local/lib/python2.7/site-packages/django/core/checks/model_checks.py", line 28, in check_all_models     errors.extend(model.check(**kwargs))   file "/var/www/cltc/env/local/lib/python2.7/site-packages/django/db/models/base.py", line 1180, in check     errors.extend(cls._check_long_column_names())   file "/var/www/cltc/env/local/lib/python2.7/site-packages/django/db/models/base.py", line 1631, in _check_long_column_names     m2m in f.remote_field.through._meta.local_fields: attributeerror: 'str' object has no attribute '_meta' 

this is, believe being caused wrong in models.py looks this:

from django.db import models django.contrib.auth.models import user django.conf import settings import datetime  django.core.exceptions import validationerror django.utils.translation import ugettext_lazy _  class category(models.model):     name = models.charfield('category', max_length=30)     age = models.integerfield('member age @ start of subscription', default=18)  class subscription(models.model):     name = models.charfield('subscription', max_length=30)     cost = models.decimalfield('price', max_digits=6, decimal_places=2, default=0.00)     start = models.datefield('start date')     end = models.datefield('end date')     category = models.manytomanyfield(         category,         through         = 'subscritptioncategory',         related_name    = 'category',         verbose_name    = 'membership category',         help_text       = 'membership categories included in subscription'         )      def __unicode__(self):         return u'%s' % (self.name)      def clean (self):         if self.start > self.end:             raise validationerror(                 _("start date must earlier end date"),                 )      def is_live(self):         if self.end >= datetime.datetime.now().date():             return true         else:             return false  class subscriptioncategory (models.model):     subscription = models.foreignkey(         subscription,         verbose_name    = 'subscription',         help_text       = 'a class of membership (which include several members, eg family).',     )     category = models.foreignkey(         category,         verbose_name    = 'category',         help_text       = 'a class of member (eg adult)',     ) 

any welcome

you have typo in declaration of through attribute of subscription.category: "subscritptioncategory" rather "subscriptioncategory". because of that, django can't find model you're referencing.

note since don't define fields on through model, there's not point having it; code simpler, , many of django's functions work better, if didn't define it.