AttributeError: 'NoneType' object has no attribute 'is_descendant_of'

I know, that similar issue was marked as solved few months ago, but I am experiencing this issue now again when using postgres.

Summary

I always get unhandled exeption when creating subpage or when moving some page under another one. It only happens with postgres.

Steps to reproduce

1. create basic django-cms project following the how to
2. set up the database connection to use postgresql database (Fedora 25, Postgresql 9.5)
3. create page “Home” in the admin (BTW, the wizzard, which appears, if there is no page, doesn’t work, as I can’t select the “Create page”)
4. try to create subpage of the page created in previous step

Internal Server Error: /admin/cms/page/add/
Traceback (most recent call last):
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/core/handlers/base.py", line 149, in get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/core/handlers/base.py", line 147, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/contrib/admin/options.py", line 541, in wrapper
    return self.admin_site.admin_view(view)(*args, **kwargs)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/utils/decorators.py", line 149, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/views/decorators/cache.py", line 57, in _wrapped_view_func
    response = view_func(request, *args, **kwargs)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/contrib/admin/sites.py", line 244, in inner
    return view(request, *args, **kwargs)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/cms/admin/pageadmin.py", line 374, in add_view
    return super(PageAdmin, self).add_view(request, form_url, extra_context=extra_context)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/contrib/admin/options.py", line 1437, in add_view
    return self.changeform_view(request, None, form_url, extra_context)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/utils/decorators.py", line 67, in _wrapper
    return bound_func(*args, **kwargs)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/utils/decorators.py", line 149, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/utils/decorators.py", line 63, in bound_func
    return func.__get__(self, type(self))(*args2, **kwargs2)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/utils/decorators.py", line 184, in inner
    return func(*args, **kwargs)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/django/contrib/admin/options.py", line 1378, in changeform_view
    self.save_model(request, new_object, form, not add)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/cms/admin/pageadmin.py", line 167, in save_model
    obj = obj.move(target, pos=position)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/cms/models/pagemodel.py", line 1450, in move
    super(Page, self).move(target, pos)
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/treebeard/mp_tree.py", line 1046, in move
    return MP_MoveHandler(self, target, pos).process()
  File "/home/misli/testcms/django-cms-site/lib/python2.7/site-packages/treebeard/mp_tree.py", line 444, in process
    if self.target.is_descendant_of(self.node):
AttributeError: 'NoneType' object has no attribute 'is_descendant_of'

Environment

• Python version: 2.7.13
• Django version: 1.9.12
• django CMS version: 3.4.2

appdirs==1.4.2
Django==1.9.12
django-classy-tags==0.8.0
django-cms==3.4.2
django-formtools==2.0
django-sekizai==0.10.0
django-treebeard==4.1.0
djangocms-admin-style==1.2.6.2
packaging==16.8
psycopg2==2.6.2
pyparsing==2.1.10
six==1.10.0

[misli]

Well, it took me some time, but I have finally found it. As I have written in the previous comment, the collation matters. You haven’t encountered this issue, as You probably use en_US.UTF-8 as default collation. But for different locales the default collation is also different. On system with system default locale for example (my case) cs_CZ.UTF-8 the command su - postgres -c "createdb test" creates database as following:

CREATE DATABASE test
  WITH OWNER = postgres
       ENCODING = 'UTF8'
       TABLESPACE = pg_default
       LC_COLLATE = 'cs_CZ.UTF-8'
       LC_CTYPE = 'cs_CZ.UTF-8'
       CONNECTION LIMIT = -1;

It is not wrong. I want all the names, titles, etc. to be sorted correctly (č between c and d, ch between h and i, etc.), but in case of public.cms_page.path the collation should always ensure that 0 is lower than A. Therefore i’d suggest to always use “C”. I’ll create an issue for treebeard, but some note in django-cms documentation would also be nice.

[misli]

Unfortunately, the result is the same even using the installer. Both creating a subpage or moving a page under another one fails. I’ll try to investigate, why it is happening.