Improve error response from pydantic validator

This should go away when vitalik/django-ninja#825 is resolved.

isic/core/serializers.py

@@ -7,8 +7,8 @@
 from django.shortcuts import get_object_or_404
 from isic_metadata import FIELD_REGISTRY
 from ninja import Schema
-from ninja.errors import ValidationError
 from pydantic import validator
+from pydantic_core import PydanticCustomError
 from pyparsing.exceptions import ParseException
 from rest_framework import serializers
 from rest_framework.fields import Field
@@ -103,7 +103,7 @@ def valid_search_query(cls, value: str):
         except ParseException:
             # TODO normally we should raise a ValueError, but django-ninja 1.0a2 has a bug
             # https://github.com/vitalik/django-ninja/issues/825
-            raise ValidationError(["Couldn't parse search query."])
+            raise PydanticCustomError("invalid_query", "Couldn't parse search query.")
         return value
 
     @validator("collections", pre=True)