Fixed #21375 -- related_name='+' clashed with other '+' names

            # occurs for symmetrical m2m relations to self). If this is the

            # case, there are no clashes to check for this field, as there are

            # no reverse descriptors for this field.

            if rel_name is not None:

            if not f.rel.is_hidden():

                for r in rel_opts.fields:

                    if r.name == rel_name:

                        e.add(opts, "Accessor for m2m field '%s' clashes with field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.name, f.name))

    # Testing choices= Iterable of Iterables

    #   See: https://code.djangoproject.com/ticket/20430

    thing = models.CharField(max_length=100, blank=True, choices=Things())

    class Meta:

        # Models created as unmanaged as these aren't ever queried

        managed = False

class ManyToManyRel(models.Model):

    thing1 = models.ManyToManyField(ThingWithIterableChoices, related_name='+')

    thing2 = models.ManyToManyField(ThingWithIterableChoices, related_name='+')

    class Meta:

        # Models created as unmanaged as these aren't ever queried

        managed = False

class FKRel(models.Model):

    thing1 = models.ForeignKey(ThingWithIterableChoices, related_name='+')

    thing2 = models.ForeignKey(ThingWithIterableChoices, related_name='+')

    class Meta:

        # Models created as unmanaged as these aren't ever queried

        managed = False

        # Validation Tests:

        #   * choices= Iterable of Iterables

        #       See: https://code.djangoproject.com/ticket/20430

        #   * related_name='+' doesn't clash with another '+'

        #       See: https://code.djangoproject.com/ticket/21375

        management.call_command("validate", stdout=six.StringIO())