def delPage(pageIndex, retJson=True):
    """ Delete specific page.
        Note: If there is only one page left, can not delete the page.

        @param pageIndex
        index of the page to be deleted

        @retJson
        format return value to json format or not( default True )

        @return
        a dict contains state of process, format like:
        {
            'success': True,
            'msg': 'Delete page success.'
        }

        """
