Improved the error message when trying to duplicate a Trust

apps/note/api/serializers.py

@@ -11,6 +11,7 @@ from member.models import Membership
 from note_kfet.middlewares import get_current_request
 from permission.backends import PermissionBackend
 from rest_framework.utils import model_meta
+from rest_framework.validators import UniqueTogetherValidator
 
 from ..models.notes import Note, NoteClub, NoteSpecial, NoteUser, Alias, Trust
 from ..models.transactions import TransactionTemplate, Transaction, MembershipTransaction, TemplateCategory, \
@@ -86,11 +87,9 @@ class TrustSerializer(serializers.ModelSerializer):
     class Meta:
         model = Trust
         fields = '__all__'
-
-    def validate(self, attrs):
-        instance = Trust(**attrs)
-        instance.clean()
-        return attrs
+        validators = [UniqueTogetherValidator(
+            queryset=Trust.objects.all(), fields=('trusting', 'trusted'),
+            message=_("You already have that person as a friend"))]
 
 
 class AliasSerializer(serializers.ModelSerializer):