protected function generateLocationAliases()
    {
        $tableName = static::MIGRATION_TABLE;

        if (!$this->tableExists($tableName)) {
            throw new RuntimeException(
                "Could not find main URL alias migration table '{$tableName}'. " .
                'Ensure that table exists (you will have to create it manually).'
            );
        }

        if (!$this->isTableEmpty($tableName)) {
            throw new RuntimeException("Table '{$tableName}' contains data.");
        }

        $this->doGenerateLocationAliases();
    }