Using CKEditor with Flatpages

admin.py

from django.contrib import admin
from django.contrib.flatpages.models import FlatPage

# Note: we are renaming the original Admin and Form as we import them!
from django.contrib.flatpages.admin import FlatPageAdmin as FlatPageAdminOld
from django.contrib.flatpages.admin import FlatpageForm as FlatpageFormOld

from django import forms
from ckeditor.widgets import CKEditorWidget

class FlatpageForm(FlatpageFormOld):
    content = forms.CharField(widget=CKEditorWidget())
    class Meta:
        model = FlatPage # this is not automatically inherited from FlatpageFormOld


class FlatPageAdmin(FlatPageAdminOld):
    form = FlatpageForm


# We have to unregister the normal admin, and then reregister ours
admin.site.unregister(FlatPage)
admin.site.register(FlatPage, FlatPageAdmin)

To get this to work In Django 2.0 I created a new app call projectflatpages.
Reference: https://docs.djangoproject.com/en/2.0/ref/contrib/flatpages/#via-the-admin-interface, https://docs.djangoproject.com/en/2.0/ref/contrib/admin/#django.contrib.admin.ModelAdmin.formfield_overrides

Created an admin.py in the app folder.

from django.contrib import admin
from django.db import models
from django.contrib.flatpages.admin import FlatPageAdmin
from django.contrib.flatpages.models import FlatPage
from django.utils.translation import gettext_lazy as _
from ckeditor.widgets import CKEditorWidget

# Define a new FlatPageAdmin
class FlatPageAdmin(FlatPageAdmin):
    formfield_overrides = {
        models.TextField: {'widget': CKEditorWidget}
    }

# Re-register FlatPageAdmin
admin.site.unregister(FlatPage)
admin.site.register(FlatPage, FlatPageAdmin)

To get this to work In Django 2.0 I created a new app call projectflatpages.
Reference: https://docs.djangoproject.com/en/2.0/ref/contrib/flatpages/#via-the-admin-interface, https://docs.djangoproject.com/en/2.0/ref/contrib/admin/#django.contrib.admin.ModelAdmin.formfield_overrides

Created an admin.py in the app folder.

from django.contrib import admin
from django.db import models
from django.contrib.flatpages.admin import FlatPageAdmin
from django.contrib.flatpages.models import FlatPage
from django.utils.translation import gettext_lazy as _
from ckeditor.widgets import CKEditorWidget

# Define a new FlatPageAdmin
class FlatPageAdmin(FlatPageAdmin):
    formfield_overrides = {
        models.TextField: {'widget': CKEditorWidget}
    }

# Re-register FlatPageAdmin
admin.site.unregister(FlatPage)
admin.site.register(FlatPage, FlatPageAdmin)

This works fine. thanks dude.