docs: def _get_available_versions(self):
          '''
          Get available versions of the package.
          :return:
          '''
          solvables = self.zypper.nolock.xml.call('se', '-xv', self.name).getElementsByTagName('solvable')
          if not solvables:
              raise CommandExecutionError('No packages found matching \'{0}\''.format(self.name))
  
          return sorted(set([slv.getAttribute(self._attr_solvable_version)
                             for slv in solvables if slv.getAttribute(self._attr_solvable_version)]))