code: def validate_rmq_ssl_enabled_units(self, sentry_units, port=None):
          
          for sentry_unit in sentry_units:
              if not self.rmq_ssl_is_enabled_on_unit(sentry_unit, port=port):
                  return ('Unexpected condition:  ssl is disabled on unit '
                          '({})'.format(sentry_unit.info['unit_name']))
          return None
docs: Check that ssl is enabled on rmq juju sentry units.
  
          :param sentry_units: list of all rmq sentry units
          :param port: optional ssl port override to validate
          :returns: None if successful, otherwise return error message