          self.enforce_required_fields(attrs)
          queryset = self.queryset
          queryset = self.filter_queryset(attrs, queryset)
          queryset = self.exclude_current_instance(attrs, queryset)
          if queryset.exists():
              message = self.message.format(date_field=self.date_field)
              raise ValidationError({self.field: message})
  
      def __repr__(self):
          return unicode_to_repr('<%s(queryset=%s, field=%s, date_field=%s)>' % (
 
</s> remove         if queryset.exists():
 </s> add         if qs_exists(queryset): </s> remove         if None not in checked_values and queryset.exists():
 </s> add         if None not in checked_values and qs_exists(queryset): </s> remove         return queryset.filter(**filter_kwargs)
 </s> add         return qs_filter(queryset, **filter_kwargs) </s> remove         return queryset.filter(**filter_kwargs)
 </s> add         return qs_filter(queryset, **filter_kwargs) </s> remove         return queryset.filter(**filter_kwargs)
 </s> add         return qs_filter(queryset, **filter_kwargs)
        if qs_exists(queryset):
          self.enforce_required_fields(attrs)
          queryset = self.queryset
          queryset = self.filter_queryset(attrs, queryset)
          queryset = self.exclude_current_instance(attrs, queryset)
        if qs_exists(queryset):
              message = self.message.format(date_field=self.date_field)
              raise ValidationError({self.field: message})
  
      def __repr__(self):
          return unicode_to_repr('<%s(queryset=%s, field=%s, date_field=%s)>' % (
keep keep keep keep replace keep keep keep keep keep
 Robust uniqueness checks. (#4217)

* Robust uniqueness checks
* Add master to test matrix (allow_failures) 
rest_framework/validators.py