Merge branch 'corpus-types-stale-read' into 'master'

fix corpus types stale read when creating a new element type

Closes #1021

See merge request !1688

arkindex/documents/serializers/light.py

@@ -84,8 +84,8 @@ class ElementTypeLightSerializer(serializers.ModelSerializer):
     def validate(self, data):
         slug = data.get('slug') if 'slug' in data else self.instance.slug
         corpus = data.get('corpus') if 'corpus' in data else self.instance.corpus
-        type = corpus.types.filter(slug=slug)
-        if type.exists() and (not self.instance or type.first().id != self.instance.id):
+        type = corpus.types.filter(slug=slug).using('default').first()
+        if type is not None and (not self.instance or type.id != self.instance.id):
             raise ValidationError({'slug': ['Slug must be unique']})
         return data