docs: def exec_command(self):
          """Glean the command to run and exec.
  
          On problems, sys.exit.
          This method should *never* return.
          """
          if not self.original_command_string:
              raise SSHEnvironmentError('no SSH command found; '
                                        'interactive shell disallowed.')
  
          command_info = {'from': self.get_client_ip(),
                          'keyname': self.keyname,
                          'ssh_original_comand': self.original_command_string,
                          'time': time.time()}
  
          os.environ['AUTHPROGS_KEYNAME'] = self.keyname
  
          retcode = 126
          try:
              match = self.find_match()
              command_info['command'] = match.get('command')
              self.logdebug('find_match returned "%s"\n' % match)
  
              command = match['command']
              retcode = subprocess.call(command)
              command_info['code'] = retcode
              self.log('result: %s\n' % command_info)
              sys.exit(retcode)
          except (CommandRejected, OSError) as err:
              command_info['exception'] = '%s' % err
              self.log('result: %s\n' % command_info)
              sys.exit(retcode)