Fix broken User link name (it was possible to change link name to one that was already used, validation was not working correctly).
Patch by: Pawel Solyga
from django.core.management.base import NoArgsCommand
class Command(NoArgsCommand):
help = "Validates all installed models."
requires_model_validation = False
def handle_noargs(self, **options):
self.validate(display_num_errors=True)