id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
29636	Failing admin.E108 system check in 2.1	Petr Boros	nobody	"After upgrading to Django 2.1, we have system checks failing due to `admin.E108` `SystemCheckError`. This behavior was not present in Django 2.0.8. I don't see any relevant API change documented in the 2.1 Release notes, therefore I'm filing this as a bug.

The error:
{{{
<class 'automation.admin.TriggerAdmin'>: (admin.E108) The value of 'list_display[3]' refers to 'position', which is not a callable, an attribute of 'TriggerAdmin', or an attribute or method on 'automation.Trigger'.
}}}

The `automation.admin.TriggerAdmin` class:
{{{
from django.contrib import admin
from automation.models import Trigger

@admin.register(Trigger)
class TriggerAdmin(admin.ModelAdmin):
    model = Trigger
    list_display = ('company', 'trigger_type', 'action_type', 'position')
    list_filter = ('company', 'trigger_type', 'action_type')
}}}

The `automation.models.Trigger` model (abbreviated):
{{{
from django.db import models
from core.fields import PositionField

class Trigger(models.Model):
    position = PositionField(
        verbose_name=_('Priority'),
        collection='company'
    )

    (...)
}}}

The `core.fields.PositionField` field (abbreviated, originally taken from the `django-positions` package):
{{{
from django.db import models

class PositionField(models.IntegerField):
    (...)
}}}"	Bug	closed	contrib.admin	2.1	Normal	invalid	SystemCheckError		Unreviewed	0	0	0	0	0	0