Changed django.forms.ValidationError imports to django.core.exceptions.ValidationError.

Co-Authored-By: Mariusz Felisiak <felisiak.mariusz@gmail.com>

tests/model_forms/tests.py

@@ -5,10 +5,9 @@ from unittest import mock, skipUnless
 
 from django import forms
 from django.core.exceptions import (
-    NON_FIELD_ERRORS, FieldError, ImproperlyConfigured,
+    NON_FIELD_ERRORS, FieldError, ImproperlyConfigured, ValidationError,
 )
 from django.core.files.uploadedfile import SimpleUploadedFile
-from django.core.validators import ValidationError
 from django.db import connection, models
 from django.db.models.query import EmptyQuerySet
 from django.forms.models import (
@@ -2619,7 +2618,7 @@ class CustomCleanTests(TestCase):
 
             def clean(self):
                 if not self.cleaned_data['left'] == self.cleaned_data['right']:
-                    raise forms.ValidationError('Left and right should be equal')
+                    raise ValidationError('Left and right should be equal')
                 return self.cleaned_data
 
         form = TripleFormWithCleanOverride({'left': 1, 'middle': 2, 'right': 1})