code: def get_ubuntu_release_from_sentry(self, sentry_unit):
          
          msg = None
          cmd = 'lsb_release -cs'
          release, code = sentry_unit.run(cmd)
          if code == 0:
              self.log.debug('{} lsb_release: {}'.format(
                  sentry_unit.info['unit_name'], release))
          else:
              msg = ('{} `{}` returned {} '
                     '{}'.format(sentry_unit.info['unit_name'],
                                 cmd, release, code))
          if release not in self.ubuntu_releases:
              msg = ("Release ({}) not found in Ubuntu releases "
                     "({})".format(release, self.ubuntu_releases))
          return release, msg
docs: Get Ubuntu release codename from sentry unit.
  
          :param sentry_unit: amulet sentry/service unit pointer
          :returns: list of strings - release codename, failure message