fix admin video categories

apps/core/admin.py

 from django.contrib import admin
 from django.contrib.contenttypes.admin import GenericTabularInline
 
-from . import models
+from . import models, forms
 
 
 class TagAdmin(admin.ModelAdmin):
@@ -24,8 +24,24 @@ class TagInline(GenericTabularInline):
 
 
 class VideoAdmin(admin.ModelAdmin):
+    form = forms.VideoForm
+    fields = [
+        'title',
+        'slug',
+        'status',
+        'description',
+        'local_file',
+        's3_file',
+        'thumbnail',
+        'duration',
+        'creator',
+        'closed_captions',
+        'categories',
+        'created',
+        'updated'
+    ]
     list_display = ['id', 'title', 'slug', 'status', 'duration']
-    readonly_fields = ['created', 'updated']
+    readonly_fields = ['s3_file', 'created', 'updated']
     list_filter = ('status',)
     inlines = [TagInline]
 

apps/core/forms.py

+from django.contrib.admin.widgets import FilteredSelectMultiple
+from django.forms import ModelForm
+
+from .models import Video
+
+
+class VideoForm(ModelForm):
+    class Meta:
+        model = Video
+        fields = '__all__'
+        widgets = {
+            'categories': FilteredSelectMultiple('Verbose name', False),
+        }