models: AttributeRelease.attribute_name must not be contrained at the model level

authentic2_idp_oauth2/admin.py

@@ -1,5 +1,6 @@
 from django.utils.translation import ugettext_lazy as _
 from django.contrib import admin
+from django import forms
 
 from authentic2.decorators import to_iter
 from authentic2.attributes_ng.engine import get_attribute_names
@@ -10,15 +11,20 @@ from . import models
 class WebServiceAdmin(admin.ModelAdmin):
     prepopulated_fields = {'slug': ('name',)}
 
-class AttributeReleaseInline(admin.TabularInline):
-    model = models.AttributeRelease
-
-    def formfield_for_choice_field(self, db_field, request, **kwargs):
+class AttributeReleaselineForm(forms.ModelForm):
+    class Meta:
         def choices(ctx):
             return [('', _('None'))] + get_attribute_names(ctx)
-        if db_field.name == 'attribute_name':
-            kwargs['choices'] = to_iter(choices)({'user': None, 'request': None})
-        return super(AttributeReleaseInline, self).formfield_for_choice_field(db_field, request, **kwargs)
+
+        model = models.AttributeRelease
+        widgets = {
+                'attribute_name': forms.Select(choices=to_iter(choices)({'user': None, 'request': None}))
+        }
+
+class AttributeReleaseInline(admin.TabularInline):
+    model = models.AttributeRelease
+    form = AttributeReleaselineForm
+
 
 class A2ClientAdmin(ClientAdmin):
     inlines = [AttributeReleaseInline]

authentic2_idp_oauth2/models.py

@@ -18,8 +18,7 @@ class AttributeRelease(models.Model):
     client = models.ForeignKey(A2Client, verbose_name=_('client'))
     name = models.CharField(verbose_name=_('name'), max_length=64)
     attribute_name = models.CharField(max_length=64,
-            verbose_name=_('attribute name'),
-            choices=(('', _('None')),))
+            verbose_name=_('attribute name'))
 
     class Meta:
         verbose_name = _('OAuth2 attribute release')