def METHOD_NAME(appname, modelname, fieldname):
    def _drop_index(apps, schemaEditor):
        # code based on https://docs.djangoproject.com/en/1.8/_modules/django/db/backends/base/schema/#BaseDatabaseSchemaEditor.alter_field
        model = apps.get_model(appname, modelname)
        index_names = schemaEditor._constraint_names(model, index=True)
        for index_name in index_names:
            if re.search("%s_%s_.+_like" % (modelname, fieldname), index_name):
                schemaEditor.execute(
                    schemaEditor._delete_constraint_sql(
                        schemaEditor.sql_delete_index, model, index_name
                    )
                )
    return _drop_index