MPTT model creation fails in data migration -

i have written data migration file creating initial data mptt model.

but creation fails,

def create_foo(apps, schema_editor):     db_alias = schema_editor.connection.alias     logger = logging.getlogger(__name__)      foo = apps.get_model("app", "foo")      attr in roles:         try:             foo = foo.objects.using(db_alias).get(name=attr[0])     except foo.doesnotexist:         parent = foo.objects.using(db_alias).get(name=attr[1]) if attr[1] else none         if parent:             foo = foo.objects.create(name=attr[0], parent=parent)         else:             foo = foo.objects.using(db_alias).create(name=attr[0])         logger.info("created foo - %s" % foo) 

i getting below error while executing below line, ideas?

foo = foo.objects.using(db_alias).create(name=attr[0])

file "/library/frameworks/python.framework/versions/2.7/lib/python2.7/site-packages/mysqldb/connections.py", line 36, in defaulterrorhandler raise errorclass, errorvalue django.db.utils.integrityerror: (1048, "column 'lft' cannot null")

you have manually register model mptt:

from mptt import register  def create_foo(apps, schema_editor):     db_alias = schema_editor.connection.alias     logger = logging.getlogger(__name__)      foo = apps.get_model("app", "foo")     register(foo)      # ... rest of code...