django 1.7 migrations + django-guardian

perms.py

"""
You also need to create initial migration for guardian app!
"""
from django.contrib.contenttypes.models import ContentType
from guardian.models import UserObjectPermission, GroupObjectPermission


def is_user(obj):
    return obj._meta.model_name == 'user'


def is_group(obj):
    return obj._meta.model_name == 'group'


def get_content_type(obj):
    return ContentType.objects.get_for_model(obj)


def assign_perm(apps, perm, owner, obj=None):
    """
    Accepts:
        apps: django apps registry containing historical models
        owner: user or group
    """
    Permission = apps.get_model('auth', 'Permission')
    UserObjectPermission = apps.get_model('guardian', 'UserObjectPermission')
    GroupObjectPermission = apps.get_model('guardian', 'GroupObjectPermission')
    try:
        app_label, codename = perm.split('.', 1)
    except ValueError:
        raise ValueError("perm must be in format: 'app_label.codename'")
    if obj is None:
        perm = Permission.objects.get(
            content_type__app_label=app_label,
            codename=codename)
        if is_user(owner):
            owner.user_permissions.add(perm)
            return perm
        elif is_group(owner):
            owner.permissions.add(perm)
            return perm
    else:
        perm = Permission.objects.get(
            content_type=get_content_type(obj),
            codename=codename)
        kwargs = {
            'permission': perm,
            'content_type': perm.content_type,
            'object_pk': obj.pk,
        }
        if is_user(owner):
            kwargs['user'] = owner
            return UserObjectPermission.objects.get_or_create(**kwargs)
        elif is_group(owner):
            kwargs['group'] = owner
            return GroupObjectPermission.objects.get_or_create(**kwargs)


def remove_perm(apps, perm, owner, obj=None):
    """
    Accepts:
        apps: django apps registry containing historical models
        owner: user or group
    """
    Permission = apps.get_model('auth', 'Permission')
    UserObjectPermission = apps.get_model('guardian', 'UserObjectPermission')
    GroupObjectPermission = apps.get_model('guardian', 'GroupObjectPermission')
    try:
        app_label, codename = perm.split('.', 1)
    except ValueError:
        raise ValueError("perm must be in format: 'app_label.codename'")
    if obj is None:
        perm = Permission.objects.get(
            content_type__app_label=app_label,
            codename=codename)
        if is_user(owner):
            owner.user_permissions.remove(perm)
        elif is_group(owner):
            owner.permissions.remove(perm)
    else:
        filters = {
            'permission__codename': codename,
            'permission__content_type': get_content_type(obj),
            'object_pk': obj.pk,
        }
        if is_user(owner):
            filters['user'] = owner
            UserObjectPermission.objects.filter(**filters).delete()
        elif is_group(owner):
            filters['group'] = owner
            GroupObjectPermission.objects.filter(**filters).delete()

This snippet was great. Just the ContentType model should also be retrieved by apps.get_model().