code: def validate_account_alias(iam_client, account_alias):
      
      # Super overkill here using pagination when an account can only
      # have a single alias, but at least this implementation should be
      # future-proof
      current_account_aliases = []
      paginator = iam_client.get_paginator('list_account_aliases')
      response_iterator = paginator.paginate()
      for page in response_iterator:
          current_account_aliases.extend(page.get('AccountAliases', []))
      if account_alias in current_account_aliases:
          LOGGER.info('Verified current AWS account alias matches required '
                      'alias %s.',
                      account_alias)
      else:
          LOGGER.error('Current AWS account aliases "%s" do not match '
                       'required account alias %s in Runway config.',
                       ','.join(current_account_aliases),
                       account_alias)
          sys.exit(1)
docs: Exit if list_account_aliases doesn't include account_alias.