Django 1.11.16 (LTS) and zinnia, zinnia-wysiwyg-tinymce, django-tinymce issue

[ghachey]

I get the error below when trying to upgrade Django to 1.11.16 (LTS). This is running with Python 3.6.7 the latest supported Python for Django 1.11.16 (LTS). My python env contains the following.

$ pip list
Package                 Version   
----------------------- ----------
beautifulsoup4          4.6.3     
Django                  1.11.16   
django-blog-zinnia      0.20      
django-contrib-comments 1.9.0     
django-js-asset         1.1.0     
django-mptt             0.9.1     
django-tagging          0.4.6     
django-tinymce          2.2.0     
django-xmlrpc           0.1.8     
mots-vides              2015.5.11 
Pillow                  3.4.2     
pip                     18.1      
psycopg2                2.7.5     
psycopg2-binary         2.7.5     
pyparsing               2.1.10    
pytz                    2016.10   
regex                   2016.11.21
setuptools              39.0.1    
sorl-thumbnail          12.5.0    
zinnia-wysiwyg-tinymce  1.4

The above I believe works when I had Django 1.10.8 which is no longer supported. Could zinnia and zinnia-wysiwyg-tinymce be made to work with the latest django-tinymce and Django 1.11.16 (LTS)?

$ python manage.py runserver
Unhandled exception in thread started by <function check_errors.<locals>.wrapper at 0x10c166950>
Traceback (most recent call last):
  File "/Users/ghachey/.venvs/ghachey.info/lib/python3.6/site-packages/django/utils/autoreload.py", line 228, in wrapper
    fn(*args, **kwargs)
  File "/Users/ghachey/.venvs/ghachey.info/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 116, in inner_run
    autoreload.raise_last_exception()
  File "/Users/ghachey/.venvs/ghachey.info/lib/python3.6/site-packages/django/utils/autoreload.py", line 251, in raise_last_exception
    six.reraise(*_exception)
  File "/Users/ghachey/.venvs/ghachey.info/lib/python3.6/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/Users/ghachey/.venvs/ghachey.info/lib/python3.6/site-packages/django/utils/autoreload.py", line 228, in wrapper
    fn(*args, **kwargs)
  File "/Users/ghachey/.venvs/ghachey.info/lib/python3.6/site-packages/django/__init__.py", line 27, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/Users/ghachey/.venvs/ghachey.info/lib/python3.6/site-packages/django/apps/registry.py", line 108, in populate
    app_config.import_models()
  File "/Users/ghachey/.venvs/ghachey.info/lib/python3.6/site-packages/django/apps/config.py", line 202, in import_models
    self.models_module = import_module(models_module_name)
  File "/Users/ghachey/.pyenv/versions/3.6.7/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/ghachey/.venvs/ghachey.info/lib/python3.6/site-packages/tinymce/models.py", line 6, in <module>
    from tinymce import widgets as tinymce_widgets
  File "/Users/ghachey/.venvs/ghachey.info/lib/python3.6/site-packages/tinymce/widgets.py", line 15, in <module>
    from django.forms.widgets import flatatt
ImportError: cannot import name 'flatatt'